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Monday, 26 July 2010 21:00

VII. GPLv3 License

Written by Kent Lee

Preamble

The GNU General Public License is a free, copyleft license for software and other kinds of works.

The licenses for most software and other practical works are designed to take away your freedom to share and change the works. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change all versions of a program--to make sure it remains free software for all its users. We, the Free Software Foundation, use the GNU General Public License for most of our software; it applies also to any other work released this way by its authors. You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for them if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs, and that you know you can do these things.

To protect your rights, we need to prevent others from denying you these rights or asking you to surrender the rights. Therefore, you have certain responsibilities if you distribute copies of the software, or if you modify it: responsibilities to respect the freedom of others.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must pass on to the recipients the same freedoms that you received. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

Developers that use the GNU GPL protect your rights with two steps: (1) assert copyright on the software, and (2) offer you this License giving you legal permission to copy, distribute and/or modify it.

For the developers' and authors' protection, the GPL clearly explains that there is no warranty for this free software. For both users' and authors' sake, the GPL requires that modified versions be marked as changed, so that their problems will not be attributed erroneously to authors of previous versions.

Some devices are designed to deny users access to install or run modified versions of the software inside them, although the manufacturer can do so. This is fundamentally incompatible with the aim of protecting users' freedom to change the software. The systematic pattern of such abuse occurs in the area of products for individuals to use, which is precisely where it is most unacceptable. Therefore, we have designed this version of the GPL to prohibit the practice for those products. If such problems arise substantially in other domains, we stand ready to extend this provision to those domains in future versions of the GPL, as needed to protect the freedom of users.

Finally, every program is threatened constantly by software patents. States should not allow patents to restrict development and use of software on general-purpose computers, but in those that do, we wish to avoid the special danger that patents applied to a free program could make it effectively proprietary. To prevent this, the GPL assures that patents cannot be used to render the program non-free.

The precise terms and conditions for copying, distribution and modification follow.

TERMS AND CONDITIONS

0. Definitions.

“This License” refers to version 3 of the GNU General Public License.

“Copyright” also means copyright-like laws that apply to other kinds of works, such as semiconductor masks.

“The Program” refers to any copyrightable work licensed under this License. Each licensee is addressed as “you”. “Licensees” and “recipients” may be individuals or organizations.

To “modify” a work means to copy from or adapt all or part of the work in a fashion requiring copyright permission, other than the making of an exact copy. The resulting work is called a “modified version” of the earlier work or a work “based on” the earlier work.

A “covered work” means either the unmodified Program or a work based on the Program.

To “propagate” a work means to do anything with it that, without permission, would make you directly or secondarily liable for infringement under applicable copyright law, except executing it on a computer or modifying a private copy. Propagation includes copying, distribution (with or without modification), making available to the public, and in some countries other activities as well.

To “convey” a work means any kind of propagation that enables other parties to make or receive copies. Mere interaction with a user through a computer network, with no transfer of a copy, is not conveying.

An interactive user interface displays “Appropriate Legal Notices” to the extent that it includes a convenient and prominently visible feature that (1) displays an appropriate copyright notice, and (2) tells the user that there is no warranty for the work (except to the extent that warranties are provided), that licensees may convey the work under this License, and how to view a copy of this License. If the interface presents a list of user commands or options, such as a menu, a prominent item in the list meets this criterion.

1. Source Code.

The “source code” for a work means the preferred form of the work for making modifications to it. “Object code” means any non-source form of a work.

A “Standard Interface” means an interface that either is an official standard defined by a recognized standards body, or, in the case of interfaces specified for a particular programming language, one that is widely used among developers working in that language.

The “System Libraries” of an executable work include anything, other than the work as a whole, that (a) is included in the normal form of packaging a Major Component, but which is not part of that Major Component, and (b) serves only to enable use of the work with that Major Component, or to implement a Standard Interface for which an implementation is available to the public in source code form. A “Major Component”, in this context, means a major essential component (kernel, window system, and so on) of the specific operating system (if any) on which the executable work runs, or a compiler used to produce the work, or an object code interpreter used to run it.

The “Corresponding Source” for a work in object code form means all the source code needed to generate, install, and (for an executable work) run the object code and to modify the work, including scripts to control those activities. However, it does not include the work's System Libraries, or general-purpose tools or generally available free programs which are used unmodified in performing those activities but which are not part of the work. For example, Corresponding Source includes interface definition files associated with source files for the work, and the source code for shared libraries and dynamically linked subprograms that the work is specifically designed to require, such as by intimate data communication or control flow between those subprograms and other parts of the work.

The Corresponding Source need not include anything that users can regenerate automatically from other parts of the Corresponding Source.

The Corresponding Source for a work in source code form is that same work.

2. Basic Permissions.

All rights granted under this License are granted for the term of copyright on the Program, and are irrevocable provided the stated conditions are met. This License explicitly affirms your unlimited permission to run the unmodified Program. The output from running a covered work is covered by this License only if the output, given its content, constitutes a covered work. This License acknowledges your rights of fair use or other equivalent, as provided by copyright law.

You may make, run and propagate covered works that you do not convey, without conditions so long as your license otherwise remains in force. You may convey covered works to others for the sole purpose of having them make modifications exclusively for you, or provide you with facilities for running those works, provided that you comply with the terms of this License in conveying all material for which you do not control copyright. Those thus making or running the covered works for you must do so exclusively on your behalf, under your direction and control, on terms that prohibit them from making any copies of your copyrighted material outside their relationship with you.

Conveying under any other circumstances is permitted solely under the conditions stated below. Sublicensing is not allowed; section 10 makes it unnecessary.

3. Protecting Users' Legal Rights From Anti-Circumvention Law.

No covered work shall be deemed part of an effective technological measure under any applicable law fulfilling obligations under article 11 of the WIPO copyright treaty adopted on 20 December 1996, or similar laws prohibiting or restricting circumvention of such measures.

When you convey a covered work, you waive any legal power to forbid circumvention of technological measures to the extent such circumvention is effected by exercising rights under this License with respect to the covered work, and you disclaim any intention to limit operation or modification of the work as a means of enforcing, against the work's users, your or third parties' legal rights to forbid circumvention of technological measures.

4. Conveying Verbatim Copies.

You may convey verbatim copies of the Program's source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice; keep intact all notices stating that this License and any non-permissive terms added in accord with section 7 apply to the code; keep intact all notices of the absence of any warranty; and give all recipients a copy of this License along with the Program.

You may charge any price or no price for each copy that you convey, and you may offer support or warranty protection for a fee.

5. Conveying Modified Source Versions.

You may convey a work based on the Program, or the modifications to produce it from the Program, in the form of source code under the terms of section 4, provided that you also meet all of these conditions:

  • a) The work must carry prominent notices stating that you modified it, and giving a relevant date.
  • b) The work must carry prominent notices stating that it is released under this License and any conditions added under section 7. This requirement modifies the requirement in section 4 to “keep intact all notices”.
  • c) You must license the entire work, as a whole, under this License to anyone who comes into possession of a copy. This License will therefore apply, along with any applicable section 7 additional terms, to the whole of the work, and all its parts, regardless of how they are packaged. This License gives no permission to license the work in any other way, but it does not invalidate such permission if you have separately received it.
  • d) If the work has interactive user interfaces, each must display Appropriate Legal Notices; however, if the Program has interactive interfaces that do not display Appropriate Legal Notices, your work need not make them do so.

A compilation of a covered work with other separate and independent works, which are not by their nature extensions of the covered work, and which are not combined with it such as to form a larger program, in or on a volume of a storage or distribution medium, is called an “aggregate” if the compilation and its resulting copyright are not used to limit the access or legal rights of the compilation's users beyond what the individual works permit. Inclusion of a covered work in an aggregate does not cause this License to apply to the other parts of the aggregate.

6. Conveying Non-Source Forms.

You may convey a covered work in object code form under the terms of sections 4 and 5, provided that you also convey the machine-readable Corresponding Source under the terms of this License, in one of these ways:

  • a) Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by the Corresponding Source fixed on a durable physical medium customarily used for software interchange.
  • b) Convey the object code in, or embodied in, a physical product (including a physical distribution medium), accompanied by a written offer, valid for at least three years and valid for as long as you offer spare parts or customer support for that product model, to give anyone who possesses the object code either (1) a copy of the Corresponding Source for all the software in the product that is covered by this License, on a durable physical medium customarily used for software interchange, for a price no more than your reasonable cost of physically performing this conveying of source, or (2) access to copy the Corresponding Source from a network server at no charge.
  • c) Convey individual copies of the object code with a copy of the written offer to provide the Corresponding Source. This alternative is allowed only occasionally and noncommercially, and only if you received the object code with such an offer, in accord with subsection 6b.
  • d) Convey the object code by offering access from a designated place (gratis or for a charge), and offer equivalent access to the Corresponding Source in the same way through the same place at no further charge. You need not require recipients to copy the Corresponding Source along with the object code. If the place to copy the object code is a network server, the Corresponding Source may be on a different server (operated by you or a third party) that supports equivalent copying facilities, provided you maintain clear directions next to the object code saying where to find the Corresponding Source. Regardless of what server hosts the Corresponding Source, you remain obligated to ensure that it is available for as long as needed to satisfy these requirements.
  • e) Convey the object code using peer-to-peer transmission, provided you inform other peers where the object code and Corresponding Source of the work are being offered to the general public at no charge under subsection 6d.

A separable portion of the object code, whose source code is excluded from the Corresponding Source as a System Library, need not be included in conveying the object code work.

A “User Product” is either (1) a “consumer product”, which means any tangible personal property which is normally used for personal, family, or household purposes, or (2) anything designed or sold for incorporation into a dwelling. In determining whether a product is a consumer product, doubtful cases shall be resolved in favor of coverage. For a particular product received by a particular user, “normally used” refers to a typical or common use of that class of product, regardless of the status of the particular user or of the way in which the particular user actually uses, or expects or is expected to use, the product. A product is a consumer product regardless of whether the product has substantial commercial, industrial or non-consumer uses, unless such uses represent the only significant mode of use of the product.

“Installation Information” for a User Product means any methods, procedures, authorization keys, or other information required to install and execute modified versions of a covered work in that User Product from a modified version of its Corresponding Source. The information must suffice to ensure that the continued functioning of the modified object code is in no case prevented or interfered with solely because modification has been made.

If you convey an object code work under this section in, or with, or specifically for use in, a User Product, and the conveying occurs as part of a transaction in which the right of possession and use of the User Product is transferred to the recipient in perpetuity or for a fixed term (regardless of how the transaction is characterized), the Corresponding Source conveyed under this section must be accompanied by the Installation Information. But this requirement does not apply if neither you nor any third party retains the ability to install modified object code on the User Product (for example, the work has been installed in ROM).

The requirement to provide Installation Information does not include a requirement to continue to provide support service, warranty, or updates for a work that has been modified or installed by the recipient, or for the User Product in which it has been modified or installed. Access to a network may be denied when the modification itself materially and adversely affects the operation of the network or violates the rules and protocols for communication across the network.

Corresponding Source conveyed, and Installation Information provided, in accord with this section must be in a format that is publicly documented (and with an implementation available to the public in source code form), and must require no special password or key for unpacking, reading or copying.

7. Additional Terms.

“Additional permissions” are terms that supplement the terms of this License by making exceptions from one or more of its conditions. Additional permissions that are applicable to the entire Program shall be treated as though they were included in this License, to the extent that they are valid under applicable law. If additional permissions apply only to part of the Program, that part may be used separately under those permissions, but the entire Program remains governed by this License without regard to the additional permissions.

When you convey a copy of a covered work, you may at your option remove any additional permissions from that copy, or from any part of it. (Additional permissions may be written to require their own removal in certain cases when you modify the work.) You may place additional permissions on material, added by you to a covered work, for which you have or can give appropriate copyright permission.

Notwithstanding any other provision of this License, for material you add to a covered work, you may (if authorized by the copyright holders of that material) supplement the terms of this License with terms:

  • a) Disclaiming warranty or limiting liability differently from the terms of sections 15 and 16 of this License; or
  • b) Requiring preservation of specified reasonable legal notices or author attributions in that material or in the Appropriate Legal Notices displayed by works containing it; or
  • c) Prohibiting misrepresentation of the origin of that material, or requiring that modified versions of such material be marked in reasonable ways as different from the original version; or
  • d) Limiting the use for publicity purposes of names of licensors or authors of the material; or
  • e) Declining to grant rights under trademark law for use of some trade names, trademarks, or service marks; or
  • f) Requiring indemnification of licensors and authors of that material by anyone who conveys the material (or modified versions of it) with contractual assumptions of liability to the recipient, for any liability that these contractual assumptions directly impose on those licensors and authors.

All other non-permissive additional terms are considered “further restrictions” within the meaning of section 10. If the Program as you received it, or any part of it, contains a notice stating that it is governed by this License along with a term that is a further restriction, you may remove that term. If a license document contains a further restriction but permits relicensing or conveying under this License, you may add to a covered work material governed by the terms of that license document, provided that the further restriction does not survive such relicensing or conveying.

If you add terms to a covered work in accord with this section, you must place, in the relevant source files, a statement of the additional terms that apply to those files, or a notice indicating where to find the applicable terms.

Additional terms, permissive or non-permissive, may be stated in the form of a separately written license, or stated as exceptions; the above requirements apply either way.

8. Termination.

You may not propagate or modify a covered work except as expressly provided under this License. Any attempt otherwise to propagate or modify it is void, and will automatically terminate your rights under this License (including any patent licenses granted under the third paragraph of section 11).

However, if you cease all violation of this License, then your license from a particular copyright holder is reinstated (a) provisionally, unless and until the copyright holder explicitly and finally terminates your license, and (b) permanently, if the copyright holder fails to notify you of the violation by some reasonable means prior to 60 days after the cessation.

Moreover, your license from a particular copyright holder is reinstated permanently if the copyright holder notifies you of the violation by some reasonable means, this is the first time you have received notice of violation of this License (for any work) from that copyright holder, and you cure the violation prior to 30 days after your receipt of the notice.

Termination of your rights under this section does not terminate the licenses of parties who have received copies or rights from you under this License. If your rights have been terminated and not permanently reinstated, you do not qualify to receive new licenses for the same material under section 10.

9. Acceptance Not Required for Having Copies.

You are not required to accept this License in order to receive or run a copy of the Program. Ancillary propagation of a covered work occurring solely as a consequence of using peer-to-peer transmission to receive a copy likewise does not require acceptance. However, nothing other than this License grants you permission to propagate or modify any covered work. These actions infringe copyright if you do not accept this License. Therefore, by modifying or propagating a covered work, you indicate your acceptance of this License to do so.

10. Automatic Licensing of Downstream Recipients.

Each time you convey a covered work, the recipient automatically receives a license from the original licensors, to run, modify and propagate that work, subject to this License. You are not responsible for enforcing compliance by third parties with this License.

An “entity transaction” is a transaction transferring control of an organization, or substantially all assets of one, or subdividing an organization, or merging organizations. If propagation of a covered work results from an entity transaction, each party to that transaction who receives a copy of the work also receives whatever licenses to the work the party's predecessor in interest had or could give under the previous paragraph, plus a right to possession of the Corresponding Source of the work from the predecessor in interest, if the predecessor has it or can get it with reasonable efforts.

You may not impose any further restrictions on the exercise of the rights granted or affirmed under this License. For example, you may not impose a license fee, royalty, or other charge for exercise of rights granted under this License, and you may not initiate litigation (including a cross-claim or counterclaim in a lawsuit) alleging that any patent claim is infringed by making, using, selling, offering for sale, or importing the Program or any portion of it.

11. Patents.

A “contributor” is a copyright holder who authorizes use under this License of the Program or a work on which the Program is based. The work thus licensed is called the contributor's “contributor version”.

A contributor's “essential patent claims” are all patent claims owned or controlled by the contributor, whether already acquired or hereafter acquired, that would be infringed by some manner, permitted by this License, of making, using, or selling its contributor version, but do not include claims that would be infringed only as a consequence of further modification of the contributor version. For purposes of this definition, “control” includes the right to grant patent sublicenses in a manner consistent with the requirements of this License.

Each contributor grants you a non-exclusive, worldwide, royalty-free patent license under the contributor's essential patent claims, to make, use, sell, offer for sale, import and otherwise run, modify and propagate the contents of its contributor version.

In the following three paragraphs, a “patent license” is any express agreement or commitment, however denominated, not to enforce a patent (such as an express permission to practice a patent or covenant not to sue for patent infringement). To “grant” such a patent license to a party means to make such an agreement or commitment not to enforce a patent against the party.

If you convey a covered work, knowingly relying on a patent license, and the Corresponding Source of the work is not available for anyone to copy, free of charge and under the terms of this License, through a publicly available network server or other readily accessible means, then you must either (1) cause the Corresponding Source to be so available, or (2) arrange to deprive yourself of the benefit of the patent license for this particular work, or (3) arrange, in a manner consistent with the requirements of this License, to extend the patent license to downstream recipients. “Knowingly relying” means you have actual knowledge that, but for the patent license, your conveying the covered work in a country, or your recipient's use of the covered work in a country, would infringe one or more identifiable patents in that country that you have reason to believe are valid.

If, pursuant to or in connection with a single transaction or arrangement, you convey, or propagate by procuring conveyance of, a covered work, and grant a patent license to some of the parties receiving the covered work authorizing them to use, propagate, modify or convey a specific copy of the covered work, then the patent license you grant is automatically extended to all recipients of the covered work and works based on it.

A patent license is “discriminatory” if it does not include within the scope of its coverage, prohibits the exercise of, or is conditioned on the non-exercise of one or more of the rights that are specifically granted under this License. You may not convey a covered work if you are a party to an arrangement with a third party that is in the business of distributing software, under which you make payment to the third party based on the extent of your activity of conveying the work, and under which the third party grants, to any of the parties who would receive the covered work from you, a discriminatory patent license (a) in connection with copies of the covered work conveyed by you (or copies made from those copies), or (b) primarily for and in connection with specific products or compilations that contain the covered work, unless you entered into that arrangement, or that patent license was granted, prior to 28 March 2007.

Nothing in this License shall be construed as excluding or limiting any implied license or other defenses to infringement that may otherwise be available to you under applicable patent law.

12. No Surrender of Others' Freedom.

If conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot convey a covered work so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not convey it at all. For example, if you agree to terms that obligate you to collect a royalty for further conveying from those to whom you convey the Program, the only way you could satisfy both those terms and this License would be to refrain entirely from conveying the Program.

13. Use with the GNU Affero General Public License.

Notwithstanding any other provision of this License, you have permission to link or combine any covered work with a work licensed under version 3 of the GNU Affero General Public License into a single combined work, and to convey the resulting work. The terms of this License will continue to apply to the part which is the covered work, but the special requirements of the GNU Affero General Public License, section 13, concerning interaction through a network will apply to the combination as such.

14. Revised Versions of this License.

The Free Software Foundation may publish revised and/or new versions of the GNU General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

Each version is given a distinguishing version number. If the Program specifies that a certain numbered version of the GNU General Public License “or any later version” applies to it, you have the option of following the terms and conditions either of that numbered version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of the GNU General Public License, you may choose any version ever published by the Free Software Foundation.

If the Program specifies that a proxy can decide which future versions of the GNU General Public License can be used, that proxy's public statement of acceptance of a version permanently authorizes you to choose that version for the Program.

Later license versions may give you additional or different permissions. However, no additional obligations are imposed on any author or copyright holder as a result of your choosing to follow a later version.

15. Disclaimer of Warranty.

THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

16. Limitation of Liability.

IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MODIFIES AND/OR CONVEYS THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

17. Interpretation of Sections 15 and 16.

If the disclaimer of warranty and limitation of liability provided above cannot be given local legal effect according to their terms, reviewing courts shall apply local law that most closely approximates an absolute waiver of all civil liability in connection with the Program, unless a warranty or assumption of liability accompanies a copy of the Program in return for a fee.

END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively state the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.

    JavaScript Remote Socket - Browser to Browser Communication
Copyright (C) 2010 Kent Lee

This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.

Also add information on how to contact you by electronic and paper mail.

If the program does terminal interaction, make it output a short notice like this when it starts in an interactive mode:

    JavaScript Remote Socket  Copyright (C) 2010 Kent Lee
This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'.
This is free software, and you are welcome to redistribute it
under certain conditions; type `show c' for details.

The hypothetical commands `show w' and `show c' should show the appropriate parts of the General Public License. Of course, your program's commands might be different; for a GUI interface, you would use an “about box”.

You should also get your employer (if you work as a programmer) or school, if any, to sign a “copyright disclaimer” for the program, if necessary. For more information on this, and how to apply and follow the GNU GPL, see <http://www.gnu.org/licenses/>.

The GNU General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License. But first, please read <http://www.gnu.org/philosophy/why-not-lgpl.html>.

This file is part of Javascript Remote Socket.

Javascript Remote Socket is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Javascript Remote Socket is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Javascript Remote Socket.  If not, see <http://www.gnu.org/licenses/>.This file is part of Javascript Remote Socket.

Javascript Remote Socket is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Javascript Remote Socket is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Javascript Remote Socket.  If not, see <http://www.gnu.org/licenses/>.
Monday, 26 July 2010 20:13

VI. Server

Written by Kent Lee

Most of the time, you won’t touching the server unless you wanted to do some major customization. The server simply forward the message and control the heartbeat connection of each client.

 

a. Adding custom server functions

Open up the /Server/Function.php. The functions which declared as public are able to be called by the client. To define your own server function, just add it like this:

class Jsrs_Server_Function
{
   // Existing function here...
   
   // New function here...
   public function myFunction(Jsrs_Server_Message_Client $msg, Jsrs_Server_Connection $connection, $params = array())
   {
       // Your function body here.
       // Send back your result through the $connection object.
       $connection->send($messageObject);
   }
}


The first parameter must be the client’s message object. Please refer to the API for details about what you can do with the Jsrs_Server_Message_Client object.

The second parameter will be the client’s connection object. This object hold the connection resources that allowed you to send message back to the client.

The last parameter is the function’s parameters passed by the client. It is optional. The parameter is an associative array. If the client did not specify the key of the value, the index of the array will be numeric in ascending order starting from 0. Eg: $params[0], $params[1], ....

 

Customizing server function required extensive knowledge on how JsRS works. It is better for you to familar with the whole framework before doing the customization.

 

b. Function APIs

Below is the list of functions available from the server. Please note that the parameters is the required parameter from the client.

Function’s name Parameter(s) Description Result
connect N/A Connect and register the client to the server. Event: onConnected(newClient, clientId)
disconnect N/A Disconnect the client and it’s connections. Event: onDisconnected()
getConnectedClients N/A Get a list of all connected client. Result:
array(
“result” => array(
“id” => <id>,
“info” => array()
)
)
listen N/A Listening on the server. There will be no immediate result send back. It will hold the connection until there is a message for this client or expired.
replyCallback i.) message_id - The ID used to reference for the callback message.
ii.) result - The result value that going to send back.
To return the result back to the sender. Boolean. True upon successful.
plus Array of numbers. Eg: array(1, 2, 5, 23,...) This is a test function to do a summation of all the numbers provided in the database. Result:
array(
“result” => <number>
)
Monday, 26 July 2010 20:00

V. Proxy Controlling

Written by Kent Lee

a. What is a proxy

The proxy is the middleman between your client and the server. It gives you the ability to control what your client can do. The proxy is a PHP file. Your client (JavaScript) will send a HTTP request to this proxy and call the remote function on the other client through the XHR(Ajax) transport.

 

The proxy file will place within your application so that it can access your session data to determine the client’s ID. At current stage, the proxy only supports PHP application.

 

b. Extending proxy class

By default, there a file called proxy.php which already extended the proxy class (Jsrs_Proxy_Abstract) with the class name, “Standard”. The only function you need to override is the “_getClient” function.

 

This function is used to determine the type of client should be instantiate when the request was made. Because the proxy will be called by your client (JavaScript), you can determine the type of client by checking the session. For example Administrator, Author, Member or Normal User.

You can determine by using your session data:

protected function _getClient()
{
   switch ($_SESSION['user_type']) {
       "admin":
           return "Jsrs_Proxy_Client_Admin";
       "author":
           return "Jsrs_Proxy_Client_Author";
       "member":
           return "Jsrs_Proxy_Client_Member";
       default:
           return "Jsrs_Proxy_Client_User";
   }
}


The function is accessing the session data and determines the user’s type. Of course, this might different depends on your application. The function must return either the full class name or the client object itself. The client object must be child class from Jsrs_Proxy_Client_Abstract. Read on the next section on defining user’s type.

You can override the default property that defined in the Jsrs_Proxy_Abstract class too:

class Standard extends Jsrs_Proxy_Abstract
{
   protected $_host = "192.168.0.1";
   protected $_port = 12345;
   protected $_defaultPermissive = "denied";
}


If your JsRS server was hosted in another server, you might want to replace it with the IP address or the host name. You can change the listening port number if your server is listening at different port number. The $_defaultPermissive is to determine whether a message should be rejecting if the permission function was not defined (eg: sfPlus, cfSayHello). If you set to “denied”, means any server or client remote function that without defining the permission control function, will be rejected. By default, this value is “allowed”.

 

c. Defining the user's type

You might need to define the types of user that connected to your live application. By defining the user’s type, you can set the permission of each function for each type of user. By default, the “Standard” user class was defined for you. You must define at least 1 user type in order to run JsRS. For instance you wished to define a member user type:

class Jsrs_Proxy_Client_Member extends Jsrs_Proxy_Client_Abstract
{
    public function cfRedirect()
    {
        return false;
    }

    public function sfPlus()
    {
        return false;
    }
}



You should save this class file as Member.php under /proxy/client/. This proxy will prevent the Member type of user to call a remote function name “redirect”. Note the prefix in front of the function. “cf” is refer to client function, while “sf” is refer to server function. The users with Member type are NOT able to call the server function “plus” too. Any non-false value returned will allowed the message being pass through the proxy and send to the server. Throwing an exception will caused the message being reject:

public function sfPlus()
{
   throw new Jsrs_Proxy_Exception(“Message here”, “Title here”, 100);
}

 

Throwing the proxy exception (Jsrs_Proxy_Exception) will invoke the exception handler in the client (exceptionHandler). You can throw any other exception object such as RuntimeException or Exception, these exceptional objects will NOT invoke the exceptionHandler function in the client script.

Beside of controlling the remote function, you can control the event received too:

public function onClientConnected($client)
{
   if (false === in_array($client[“id”], $friendList)) {
       return false;
   }
}


The function above will check whether the connected client is actually in the friend list or not. If not, it will not send the event to the client (JavaScript) and thus, the “onClientConnected” event will NOT fired. Put this function inside your client class to control the event happened.

Note: For those functions that did not defined in your client class, by default, the message will be received or sent through. You can change this behavior by overriding the default value of $_defaultPermissive to “denied” in the Jsrs_Proxy_Abstract class.

d. Helpers

i. Introduction

The Helper class is to reduce the needs of extending your client class in order to perform some custom functionality. Most of the time, you might focus on the client class file (Jsrs_Proxy_Client_Class). For some client remote function, you might want to check the permission based on the MySQL database. Building the database connection on each client class is very troublesome neither extending your client class is a good idea too. What the Helper class can offer you is to allow you to define a class that access to the MySQL database and call it from your client class like this:

class Jsrs_Proxy_Client_Member extends Jsrs_Proxy_Client_Abstract
{
     public function cfSayHello()
     {
         return $this->_helper->IsAdmin($_SESSION[“user_id”]);
     }
}

 

You can use this helper “IsAdmin” on any client class with the same statement. Please be careful with the helper name, the first character must be capital letter and the name must be exactly same as the Helper class file.

 

The $_helper object is defined in the Jsrs_Proxy_Client_Abstract. You don’t have to worry about it. Just call it directly to get your result.

ii. The ServerBorker helper

By default, there is one helper class, “ServerBroker”. You can use this to invoke any server’s function without connecting to the server. The result returned is in array format. To call the function, you need at least one parameter which is the server’s function name. The second parameter has to be an array which represents your parameter. The parameter array can be an associative array. Example:

array(
    "parameter1" => "value1",
    "parameter2" => "value2"
)

 

To make a server function call, do this:

$result = $this->_helper->ServerBroker("plus", array(8, 50, 30));

The $result will return you an associative array with this value:

array(
    "result" => 88
)


Notice on how the parameter being passed. You have to put all the value in the array and pass the array in the second parameter of the Helper class.

iii. Creating your own Helper class

You must place your Helper class under /Proxy/Helper and your Helper class must inherit from Jsrs_Proxy_Helper_Abstract. You have to override the “run” method in order to perform your custom task. The “run” function is the default function when calling a Helper class:

$this->_helper->HelperClassName();
// Equivalent to Jsrs_Proxy_Helper_HelperClassName::run()

 

For instance you want to define a MySQL database accessing Helper, you created a Helper class file named Jsrs_Proxy_Helper_IsAdmin.php in /Proxy/Helper:

class Jsrs_Proxy_Helper_IsAdmin extends Jsrs_Proxy_Helper_Abstract
{
    public function run()
    {
        // Do your SQL connection and Query and return the Result.
    }
}

 

You can always extends your Helper class. For example you have few Helper class that needs to access to MySQL database, you can create a MySQL Helper class that will automatically connect to the database once the Helper class was called. Then you will extends those Helper that needs to access the database from this parent class.

Sunday, 25 July 2010 23:28

IV. Client-side scripting

Written by Kent Lee

a. Instantiation and initialization

Just like any client-server application, you need to connect to the server in order to utilize the services. But this time, you will connect it in JavaScript. First include the JsRS library to your html file. Put this line in your head section.

<head>
  […]
  <script language="JavaScript" type="text/javascript" src="/javascript/jsrs.js"></script>
</head>

Now you need to instantiate a socket object from the JsRS library. You can put this code right after the opening <body> tag or you can wrap it up within a function and call it later (onclick from a button).

<script language="JavaScript" type="text/javascript">
var socket = new Jsrs({
    "proxy" : "Proxy/proxy.php",
    "cf" : {
        "functionName" : function(client, param1, param2) {
            // Your remote function body here.
        }
    },
    "events" : {
        "onConnected" : function(newClient, clientId) {
            // When you’ve successfully connected.
        },
        "onDisconnected" : function() {
            // When you’ve disconnected unexpectedly.
        },
        "onClientConnected" : function(client) {
            // When a new client connected.
            // client["id"] will return you the ID.
        },
        "onClientDisconnected" : function(client) {
            // When a client disconnected.
            // client["id"] will return you the ID.
        }
    }
});
socket.connect();
</script>

The codes above will instantiate the socket object and initialize it with the proxy path, the event handler and the remote function or the common function.

The functions that stored in the "events" object is used to handle when a certain event is fired. For example the "onConnected" function will be called when the connection was successfully established. The parameters inside the event function is passed by the server. The first parameter (newClient) is a boolean value to determine whether you are a new client or not. Because in some case, a user might open few tab or window of a same browser. JsRS is able tell that they are the same client through their session’s ID or client’s ID (Depends on your application). The second parameter (clientId) is the ID of the client that connected to the server. It is like a IP address.

For functions that stored in "cf" is the remote functions. Those are the functions that able to call by other clients. For your understanding, those function inside "cf" is like an event. They must be call by other client in order to run the function.

 

b. Basic remote scripting

Before you calling a remote function, you must define it. You can define the remote function either during the initialization or runtime:
Initialization:

var socket = new Jsrs({
    "cf" : {
        "sayHello" : function(client, message) {
            alert(client["id"] + " has sent you a message: " + message);
        }
    }
});

Runtime:

socket.cf.sayHello = function(client, message) {
    alert(client["id"] + " has sent you a message: " + message);
};

Both are having the same result. Once you have defined the remote function, you can call it using the client remote calling function, "callCF".
Note: The first parameter is always the client’s (sender) object. The basic element is "id". You may get more info of the client through the "info" property. Eg: client["info"].

i. Client remote function

Calling a remote function is very simple. You have to specify the recipient’s ID and the function name.

socket.callCF(client, funcName, [[params], callback]);

The third and fourth parameters are optional. You must provide array for the first parameter even though there is only one recipient. Example:

socket.callCF([12], "sayHello", ["Hi there!"]);


Same goes to the function’s parameters, the third one. You must provide array even though it is only one parameter for the function. The acceptable parameter types are object, string, number and array.

The code above will call the remote client with the ID: 12 to invoke the remote function "sayHello" and passed the string "Hi there!" to the second parameter.

ii. Server remote function

Under certain circumstances, you might want to retrieve information from the server. Please refer to the Server’s APIs for more details. It is very similar to calling a client remote function:

socket.callSF(funcName, [[params], callback]);

 

You have to specify the function’s name that you want to call on the server. Example:

socket.callSF("plus", [10, 70], function(result) {
 alert("The result is: " + result);
});

The function "plus" is a test function from the server which take the parameters passed by you and do a summation. The returned result will be 80. If the message was successfully passed, you should received an alert message, "The result is 80".
Note: The function parameter has to be an array even though it’s only has one parameter.

 

c. Getting remote clients

Without the client’s ID, you can’t do any remote scripting. It is depend on what application you are writing and it will affect on how you store your client’s ID. I will explain how you going to get the client’s ID but I ain’t going to talk about how you store it.

There are two way you can get the connected clients: (1) Calling server functions, (2) Event functions.
Currently, there is one server function named: "getConnectedClients". This will return you a list of clients with their ID and info. With this, you can get the connected clients. Again, depends on your application on where you want to store them.

socket.callSF("getConnectedClients", function(clients) {
    for (var i in clients) {
        var client = clients[i];
        var clientId = client["id"];
        var clientInfo = client["info"];  // This is optional and might different depend on your application.
    }
});


The second way is the event. Through the event, you can get the newly connected client. Jsrs::events::onClientConnected allowed you to handle when there are new clients connected. With this, you can update the list of connected clients in your application (JavaScript). Of course, you might need to keep track of disconnected clients, Jsrs::events.onClientDisconnected allowed you to handle when there is a client disconnected from the server. Please refer to the API for more details.

 

d. Returning data from remote function

In section b. ii., you know how to get the result from the server’s function. You can do the same thing for client. Meaning you send a remote function call to a specific client and ask the client to process and send back the data. For example you wanted to know the client’s name. You might need to define the remote function first:

socket.cf.getName = function(client, sendResult) {
     var name = prompt(client["id"] + " is asking your name.", "");
    if (name) {
        sendResult(name);
    }
};

The remote function above will prompt the user (using prompt function) and get the input as the result (user’s name) and then send back to the sender using the sendResult function.

If you are defining a remote function that required a callback, the last parameter is always a function for you to send back your result. Don’t get confused, lets read on first.

Now you’ve defined the remote function, it is time to call it:

socket.sendCF([12], "getName", function(clientName, client) {
     alert("The client's name ("+ client["id"] +") is: " + clientName);
});

The first and second parameters are the client’s ID and the remote function’s name respectively. Because the remote function do not required any parameter, so we skipped it. The third parameter will be your callback function.

The callback function will be invoked once the recipient processed and return back the result using "sendResult" function. The execution context within the callback function is the Jsrs instance. Meaning this.proxy will return you the proxy URL.

 

e. Event handlers

Event handlers allowed you to catch any events happened. Below is the list of event handlers:

Event’s name Parameter(s) Description
onConnected i.) newClient - To check whether you are a new client or a existing client (open new tab or window).
ii.) clientId - Your connected client’s ID.
It is happened when you’ve successfully connected to the server.
onDisconnected N/A When you get disconnected from the server.
onClientConnected i.) client - The client’s object that connected to the server. It is happened only once when the client is newly connected to the server.
onClientDisconnected i.) client - The client’s object that disconnected from the server. It is happened when none of the client connection are connected to the server.
onExpired N/A When the client’s connection expired. This is to keep the heartbeat connection stay alive.
Sunday, 25 July 2010 21:10

III. Installation guide

Written by Kent Lee

a. Download

Download the latest version of JsRS from here. Once you’ve downloaded, unzip the archive to your local drive. Eg: C:\jsrs-1.0\

 

b. File structure

I always believe that the file structure will determine how complicated your software is. So I’ll try to keep the file structuring as simple as possible. Here it is:
  • /jsrs-x.y
    • /Javascript
      • Index.html
      • jsrs.js
    • /Proxy
      • /Client
        • Abstract.php
        • Standard.php
      • /Helper
        • Abstract.php
        • ServerBroker.php
      • Abstract.php
      • Exception.php
      • Helper.php
      • proxy.php
      • Services_JSON.php
    • /Server
      • /Message
      • Client.php
      • Connection.php
      • ConnectionManager.php
      • Exception.php
      • Function.php
      • Server.php
      • Services_JSON.php
    • /license.txt
    • Release Note.txt


For Proxy and Server, the class name is according to the file structure. Example Jsrs_Proxy_Client_Abstract (class name) is placed under /Proxy/Client/Abstract.php.

Note: Where the x.y is the version number. x is the major version while the y is the minor version number.

 

c. Starting the server

Alright, it's time to make the server alive! Launch your command-line interface. Depending on which platform you using, the steps are almost the same:

Windows

  • Change directory to your extracted archive, eg:
    >cd C:\jsrs-1.0\Server\
  • Execute the server using php executable file; php.exe
    >C:\php\php.exe -q Server.php
  • Note: The example given above assumes that your php executable file are located in C:\php, it could be somewhere else.
  • If the server is running, you should see a message like this:
    2010-07-26 16:45:32 JavaScript Remote Socket is Running!
  • Note: DO NOT close the windows as the server is running.
  • You can also create a batch file to start the server. This will save your time to typing the same command line each time you starting the server.
Linux
  • Change directory to your extracted archive, eg:
    $ cd /home/user/downloads/jsrs-1.0/Server
  • Execute the server using php command; php
    $ php -q Server.php
  • If the server is running, you should see a message like this:
    2010-07-26 16:45:32 JavaScript Remote Socket is Running!
  • If you would like to run the server without typing it, edit the server.php by adding the following line in the header of the file:
    #!/usr/bin/php -q
    <?php ...
  • Make the server.php executable (chmod 755) and rename it as jsrs_server then run it:
    $ ./jsrs_server

Note: For demo purposes, we want the server screen to be shown all the time so that we know what is happening. For production, please refer to the documentation on how to configure a production server.

 

d. Testing the connection

In order to test your server whether is it working or not, copy or move the “/Proxy” folder to your web directory. Eg: C:\Inetpub\wwwroot\ (windows) or /var/www/html/ (linux).

It is depending on how you setting up your application. As long the proxy file are accessible within the domain (not cross domain, eg: www.domain1.com accessing proxy on www.domain2.com).
Copy the “jsrs.js” to your web drive too.  You may want to put it under your Javascript folder. The last item is the “index.html” under “/Javascript” folder. Place it under the same directory with your JavaScript file.
Now your directory will look like this:
  • /your-web-drive
    • /Proxy
    • /Javascript
      • jsrs.js
      • index.html
    • <all your web drive’s files and folders>


Once you’ve placed all the files accordingly, go to the URL that point to your webdrive’s root directory:
http://localhost/ your-web-drive/Javascript/index.html

 

You should see a form with buttons and textbox. With your server running, click on “Connect” button. You should see the message “Connected to server with the ID: <session ID>”. Congratulation, your socket server is working!

 

To have fun with the demo, open up another browser (must be different browser), go to the same URL, and click Connect.
The moment you clicked “Connect”, you will see the client’s ID appear on the right text list. The ID is the client that connected to the server. Select the client’s ID and click on the remote function at the bottom of the textbox.

Note: Where the x.y is the version number. x is the major version while the y is the minor version number.
Sunday, 25 July 2010 19:57

II. Requirements

Written by Kent Lee

The requirements are pretty much similar to a web server. Just need some extra configuration on the existing server and some privileges on the server.

  1. Any web server running PHP module. Eg: Apache or IIS.
  2. PHP 5 and above with socket enabled. Please refer to PHP Socket Manual.
  3. Privileges to execute command line in the server.
  4. At least 2 modern web browsers. (Firefox 3.0 and above, Internet Explorer 7 and above)

For the programming part, you must be able to understand basic JavaScript code and a very little knowledge of PHP code which allowed you to control the user’s permission.

 

It was tested on Windows XP Professional SP3, Apache 2.2. (with PHP5.2), Firefox 3.5, Internet Explorer 8, Google Chrome 5.0.

Sunday, 25 July 2010 19:31

I. Introduction

Written by Kent Lee

JsRS is a light-weight scripting library framework that allowed you to build a live web application easily. You don’t have to create any database table for this framework. All you need to do is define what functions you wished to be call remotely and define the permission in the proxy file, and your application is ready to go!

 

JsRS was built up in three parts, the Server, Proxy and the JavaScript. The server is like a message router that route the message from one client to another. All the message that transmitting between these parts is in JSON format.

Ordinary Live Application.JsRS Live Applications.

 

The diagram on the left shows most of the live web-based application which the client will send a request to the server (HTTP Server) through the XHR transport (Ajax) and wait for response. The request is actually a database query request. The requested page (.php, .jsp, .aspx or any server-side pages) will query the database to see if there is any new message for this client. The message will then return back to the client (JavaScript) and the client will do dispatching job. Whenever a client sending a message to another client, the message will be stored into the database and wait for the recipient to query and dispatch the message.

 

While the diagram on the right is how JsRS works. The client will send a HTTP request to the server page which is the proxy. The proxy is a middleman between the client and the server. It will send the requested message to the server using specific port number (default is 38380). The HTTP request will be hold (wait) by the proxy until there is a new message coming from the server to this client. Once the proxy got a new message from the server, it will send it back to the client immediately.

 

JsRS is a framework that allowed you to call JavaScript function remotely (browser to browser) and hence, it is necessary to manage the permission of each types of client. In other words, you need to control which JavaScript function can and cannot be called by the client based on their permission (types of client).

 

The JsRS proxy is used to control the user’s permission. The proxy is a PHP file that resides within your application and thus, it can access the user’s session data. With the session data, the proxy file is able to determine the type of user and determine the permission for each operation (JavaScript’s functions). All you have to do is define the permission for each types of user. Please refer to the documentation on how to define the permission in the proxy file.

 

Calling the JavaScript remote function is very simple. Simply specify the recipient’s ID (client’s ID) and the function name you wished to call:

socket.callCF([12], "sendInstantMessage", ["Hi, my name is Kent."]);

The client’s ID is the ID that the client used to connect to the server. By default, the session ID will be used as the client’s ID.

 

You have to define the function “sendInstantMessage” in the JavaScript so that the clients are able to handle this request. Once there is a client sending a remote call to this function, the function will be invoke and a message will appear, “Hi, my name is Kent.”. These remote functions are called the Common Functions or CF in short.

 

You can’t call the Common Functions if there are not existed in the client’s page (HTML page). You have to define the same functions (JavaScript functions) for all the pages so that they can call the functions that are common to each other.

 

Security might come into your concern when calling remote function. The Common Functions will store in a different context and is not stored in the global context. Meaning you don’t have to worry that other client are able to call the functions which is not part of the remote functions. For instance you have a function called “logout” which will destroy the user’s session and send the user back to the login page. Obviously you won’t put this as a remote function and causing the client being remote logout. Because the logout function was not defined in the remote function’s context, so this function will not be able to call remotely and your application is safe.

 

For more information, please read on the documentation.