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Programming Project #3 Web Server CS-3103 & CS-502 Operating Systems CS-3103 & CS-502, Summer 2006 Programming Project #3 1 Programming Assignment 1. Build a simple but real web server using sockets 2. Build a simple web client for testing your server 3. Make your server fork a process or spawn a thread for each new request CS-3103 & CS-502, Summer 2006 Programming Project #3 2 Purpose • To gain some insight into sockets and communication over networks. CS-3103 & CS-502, Summer 2006 Programming Project #3 3 Part 1 – Web Server • Create a socket() and bind() it to a port. • listen() on that port for requests • Wait for requests; upon receipt of a request – – – – – accept() the request Interpret the HTTP protocol Find and deliver the page; or return an error Close the accepted request Loop back and wait for another request • Figure out a way of exiting from the server cleanly. CS-3103 & CS-502, Summer 2006 Programming Project #3 4 Part 1 – Web Server (continued) • Command line:% server <directory> [optional port #] • Directory is prefixed to every request. – WPI directory for web pages is /www/docs • Port is port number for your server – You may specify a default port in your code, but don’t choose one to conflict with another student! – Warning: Unix does not let you reuse ports until after a reasonable waiting period (30 seconds?) • A request to your server of http://ccc4.wpi.edu:4242/admissions.html means ask the listener of port #4242 to return the file at /www/docs/admissions.html CS-3103 & CS-502, Summer 2006 Programming Project #3 5 Part 1 – Web Client • Simple test program that requests web pages and prints out their contents. • Use to see what your server is doing. • Use to see what another server is actually serving when you request the same pages. • Use it to gain insight into details of HTTP protocol CS-3103 & CS-502, Summer 2006 Programming Project #3 6 HTTP commands • Your server must interpret HTTP GET command • See written project description for examples • All command lines must end with CR/LF – i.e., in Unix \r\n • Series of HTTP commands ends with blank line – i.e., a stand alone \r\n CS-3103 & CS-502, Summer 2006 Programming Project #3 7 HTTP Response • Once you accept a command and have found the page, respond with HTTP success response 200 – See written project description – Be sure to follow with a blank line • If you cannot find or read the page, respond with HTTP error response 404 • You only need to serve real file pages. – Ignore scripts, etc. • WPI’s home page is a script. – Remember: some pages are not all text! CS-3103 & CS-502, Summer 2006 Programming Project #3 8 Sample code • See http://www.cs.wpi.edu/~cs502/s06/CodeFragments/ • Includes • sockserver.c • sockclient.c • sockreadline.c CS-3103 & CS-502, Summer 2006 Programming Project #3 9 Part 2 – Multi-process or multithreaded web server • Modify your web server to fork() a process or spawn a thread each time it receives a request. • This allows it to serve multiple requests in parallel. • Test with multiple web clients or browsers in parallel. • Be sure to clean up “zombie” processes on the fly – Use wait3() • Be sure that your server leaves time for each process to finish before exiting cleanly. CS-3103 & CS-502, Summer 2006 Programming Project #3 10 Project Submission • Project due at start of class on June 29 • (i.e., last class of the term for CS-3013 students) • Submit via turnin • command = ‘/cs/bin/turnin’ on CCC machines • classname = ‘cs502’ • assignment = ‘project3’ • Include • Code, makefiles, test files or input, test output CS-3103 & CS-502, Summer 2006 Programming Project #3 11 Format of submission • • • • • Write-up Makefile to make all, clean, each part Source code files (.c, .cpp, .h, etc) Any test cases Any output logs • All at top level: • No subfolders • No zip files CS-3103 & CS-502, Summer 2006 Programming Project #3 12