• Part 1 [15 points total]: Modify one of the Echo Client applications given in class. The new Echo Client you create should read lines from a text file specified by the user and send each line to the Echo Server in a loop. It should send each line of data that is in the file and print the data that is receives back from the server. In addition, the program should exit when it reaches the end of the file and after it receives the corresponding echo from the Echo Server for that line.
• Part 2 [15 points total]: Modify one of the Echo Server applications given in class. The new Echo Server should have two additions:
  • A [10 points]: It should process each connection until the client disconnects. In other words, the server should loop around the recv/send part until the recv returns a value of 0 bytes received. In other respects, this new Echo Server should conform to the RFC document for Echo given in class.
  • B [5 points]: It should handle multiple connections concurrently. For C/C++, this means adding usage of fork() and reaping all child processes. For Java, the use of the Thread class will be necessary.
• Part 3 [70 points total]: Write a basic web proxy that can handle the GET request method. This part requires multiple pieces to be done so I suggest working on each part separately and verify that each part works by itself. These parts are:
  • A [10 points]: Construct a routine or object that can read an HTTP/1.0 request from a socket and parse it into request-line, headers, and body (if present).
  • B [10 points]: Construct a routine or object to parse a URL string in the form http://machinename[:portnum]/pathname, where the part in [] is optional, into (1) host IP address, (2) port, and (3) path. Hostnames that fail to be resolved must return some sort of error to the calling application. You may not rely on any intrinsic Java objects that do URL parsing for you.
  • C [10 points]: Construct a routine or object to construct an HTTP/1.0 request line given a specific path for the requested object.
  • D [20 points]: Take the routines or objects constructed in the above parts and construct another routine or object that takes a given URL string, parses it to obtain host IP address and port, connects to the host on that port, and sends an HTTP/1.0 GET request for the object. Hostnames that fail to be resolved must return some sort of error to the calling application as well as connection errors, etc. You may not rely on any intrinsic Java objects that do this for you.
  • E [20 points]: Take the routines or objects constructed in the above parts and construct an application that listens on a given TCP port for HTTP/1.0 GET proxy requests to handle. This server should handle GET requests only. All other request methods should generate a 501 "Not Implemented" status. Any malformed request should generate a 400 "Bad Request" status. This includes all hostnames that fail to be resolved. Once a valid request is received, the application should use the routine or object above to connect to the web server, send a request for the object, receive the data from the web server, and forward the data back to the web client.

HTTP 1.0 Specification at http://www.w3.org/pub/WWW/Protocols/HTTP/1.0/spec.html

Extra Credit

For extra credit, make Part 3 support FTP URLs and requests [8%]. And/Or add support in Part 3 for tracking URL and webserver statistics [4%]. The proxy should display stats for URLs requested, errors, webserver IP address breakdown, etc. when it receives a SIGUSR1 signal.

Submission Guidelines