1. IE

2. Firefox

3. Persistent connections
HTTP/1.1 傳完之後不會自動斷線。
HTTP/1.0 才會自動斷線。

4. TCP Client-Server Interaction
TCP Server
socket()
bind()
TCP Client
listen()
socket()
accept()
connection establishment
connect()
data request
read()/recv()
write()/send()
data reply
write()/send()
read()/recv()
end-of-file notification
read()
close()
close()
from UNIX Network Programming Volume 1, figure 4.1

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

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

7. 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 ));

8. 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);

9. 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 }

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

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

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

13. HTTP Request GET http://network2006.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; SV1; (R1 1.3); .NET CLR )
Host: network2006.csie.org
Proxy-Connection: Keep-Alive

14. HTTP Response HTTP/1.0 200 OK Connection: close
Content-Type: text/html
ETag: " "
Accept-Ranges: bytes
Last-Modified: Fri, 17 Mar :23:08 GMT
Content-Length: 80
Date: Wed, 22 Mar :42:47 GMT
Server: lighttpd/1.4.10
Body …………………….