In this assignment, we will develop a simple multi-threaded Online Social Network.
The code that you develop in this part will serve as a basis for the following programming assignments. You must create a pair of programs (client and server). The server will act as a central repository where clients will post and access wall posts and exchange messages. All communications happen through the server. Clients establish a TCP session with the server when they become online. Clients also notify the server when they terminate.
The server code should be started with a parameter of port number. Similarly, client code should be started with parameters of user-ID, server-IP, and server-port (all separated with spaces).
The Server should use threads to handle client connections. Note that, you need to use locks to prevent concurrent writing of common data structures. Moreover, if threading pool is used, 3 bonus points will be added to the grade.
Following are the application level messages sent from/to the server using TCP sockets:
REGISTER user-ID user-name user-last-name
This command is used to register a user with user-ID in the system. The server will allow users to search for friends in this list using either user-ID, name, or last name.
This command looks up the register list for a keyword with no space. The keyword is a single word that can be user-ID, name, or last name.
RESULTS file-length XML
This is in reply to
SEARCH keyword and consists of all user-ID, name, last-name information as an XML file.
This command indicates the user with user-ID is leaving the system (sent from user to server). The server should assure the source-IP of the packet matches the user-IP before dropping the entry from the user table.
This command asks for friendship establishment by user-ID1 with another user user-ID2. The server will relay the message to the corresponding client (user-ID2) if they are online or hold it until they become online (and then relay it).
This command confirms friendship of User-ID1 by User-ID2 and allows subsequent messaging/wall posts. The server will relay the message to the corresponding client (user-ID1) if they are online or hold it until they become online (and then relay it).
This command indicates that User-ID2 does not want friendship establishment with User-ID1. The server will not relay the message to the User-ID1.
CHAT user-ID1 user-ID2 counter message
A chat exchange from user-ID1 is sent to user-ID2 with a counter that increments. Message can be up to 1024 characters and will be displayed to the user. Messages with end-of-line characters should be sent as a separate
CHAT. If user-ID2 is online, the server will keep a log of it and relay it to user-ID2; otherwise, the server will respond with
OFFLINE user-ID2. Once the message is delivered to user-ID2, the server will send a
DELIVERED user-ID2 counter to user-ID1.
POST group message
This command posts a wall post so that friends or friends of friends of the user can see it.
group can be either F or FF and message can be up to 1024 characters.
This command asks for up to 20 wall posts before time. The posts will be compiled by the server where they can be from friends or friends of friends. The user might ask for preceding posts by changing the time to the time of the oldest received post.
WALL file-length XML
This is in reply to
ENTRIES time and consists of wall updates as an XML file.
Note that, these formats are recommended (as we will not cross test). You need to implement these functionalities.
Report all major actions as the program communicates with other server/users in a file named
We assume user-IDs to be at most 32 characters without any white space characters.
When a malformed message is received report it in a log file named
You may utilize localhost (127.0.0.1 or actual IP address) to test your program by running multiple users on the same machine but within different folders (with different port numbers).
If testing on multiple machines, be sure that the machines are not behind a NAT (or within the same subnet).
You might get TCP messages in multiple segments even one byte at a time. Hence, you must check whether you have read all the message when parsing them (TCP streams).
You must submit all the source code with sufficient comments to help understand the code.
You must include in your submission a file named
Readme.txt that includes your name and a brief description of your submission, including the name of each file submitted along with a one line description of what is in the file.
If your code is not complete, tell us what works and what doesn't in
Readme.txt file. If you are submitting code that does not compile, please tell us that as well. If you borrow code from someone else, you are required to tell us about it (this must also be documented in the code itself).
Finally, feel free to include a description of any problems you had or anything else you think might be helpful to us.
You should work individually.
Your project will be tested to make sure it works properly.
Your grade will depend on the functionality and the code quality. Hence, please pay careful attention to clean, modular and extensible design as you implement the project.
There will be bonus grades for extra functionality (such as a well designed GUI) not required by the project (optional and at the discretion of the instructor).
There will be bonus for students that point to major issues or add to program structure.
This document will evolve as we discuss the project and determine communication protocols and messaging formats.
Don't wait till the last minute to start this phase!
Last updated on Feb 14, 2014