IE Firefox TCP ClientServer Interaction TCP Server socket

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Firefox

TCP Client-Server Interaction TCP Server socket() bind() TCP Client listen() socket() accept() connect() write()/send() connection establishment data request read()/recv() data reply write()/send() read()/recv() close() end-of-file notification read() close() from UNIX Network Programming Volume 1, figure 4. 1

Include Headers • #include <sys/socket. h> • #include <netinet/in. h> • #include <unistd. h> • #include <netdb. h>

Create a socket // declare a socket file descriptor int listenfd; listenfd = socket( AF_INET, SOCK_STREAM, 0 );

Bind a socket to an address // declare a int for bind()’s result int bindres; // declare a structure for address struct sockaddr_in proxyaddr; // initialize the structure memset(&proxyaddr, 0, sizeof(proxyaddr)); proxyaddr. sin_family = AF_INET; proxyaddr. sin_addr. s_addr = htonl( INADDR_ANY ); proxyaddr. sin_port = htons( 3128 ); //bind listenfd to bindres = bind( listenfd, (struct sockaddr *)&proxyaddr, sizeof( proxyaddr ));

Listen to the socket & Accept when someone connect listen( listenfd, 5000 ); while(1) { connfd = accept( listenfd, (struct sockaddr *)NULL, NULL ); // do things like read and write with connfd doit(); close(connfd); } close(listenfd);

What we have to do doit() { // 1. read request from the client // 2. parse request // 3. build another connection to the server // 4. send request to the server // 5. read response from the server // 6. close connection with the server // 7. parse response // 8. send response to the client }

How to read? • Use read() – read( fd, buf, strlen( buf ) ); • Use recv() – recv( fd, buf, strlen( buf ), 0 ); int fd = socket(…); char buf[1024]; or char *buf;

How to write? • Use write() – write( fd, buf, strlen( buf ) ); • Use send() – send( fd, buf, strlen( buf ), 0 ); int fd = socket(…); char buf[1024]; or char *buf;

How to connect to the server? int servfd = socket(…); connect( servfd, ( struct sockaddr * ) &servaddr, sizeof( servaddr ) );

HTTP Request GET http: //network 2006. csie. org/index. html HTTP/1. 0 Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/vnd. ms-excel, application/vnd. ms-powerpoint, application/msword, */* Accept-Language: zh-tw User-Agent: Mozilla/4. 0 (compatible; MSIE 6. 0; Windows NT 5. 1; SV 1; (R 1 1. 3); . NET CLR 1. 1. 4322) Host: network 2006. csie. org Proxy-Connection: Keep-Alive

HTTP Response HTTP/1. 0 200 OK Connection: close Content-Type: text/html ETag: "-376597886" Accept-Ranges: bytes Last-Modified: Fri, 17 Mar 2006 12: 23: 08 GMT Content-Length: 80 Date: Wed, 22 Mar 2006 16: 42: 47 GMT Server: lighttpd/1. 4. 10 Body ………….