本文介绍了一个简单的多线程HTTP服务器的实现过程，该服务器能够处理基本的HTTP请求，并返回静态资源如HTML、图片等文件。
转自：http://www.cppblog.com/cuijixin/archive/2008/07/02/55112.html
系统：fedora core 5
编译器：g++
实现功能：通过http协议，用浏览器查看服务器上的html,htm,jpg,jpeg,gif,png,css文件 ，或者说查看带有jpg,jpeg,gif等文件的网页，即是web~
把代码复制下来到linux里，照着后面的方法编译、运行，就可以看到一个简单的多线程服务器的效果了。
原理：
在浏览器中输入一个网址，回车之后，浏览器会向相应主机的相应端口发送一段报文，如果是http协议的（如平常看到的网页的传输协议），就会发送HTTP请求报文。下面是一个报文的例子：
Host: 127.0.0.1:8848
User-Agent: Mozilla/5.0 (X11; U; Linux i686; zh-CN; rv:1.8.0.1) Gecko/20060313 Fedora/1.5.0.1-9 Firefox/1.5.0.1 pango-text
Accept: text/xml,application/xml,application/xhtml+xml,text/html;q=0.9,text/plain;q=0.8,image/png,*/*;q=0.5
Accept-Language: zh-cn,zh;q=0.5
Accept-Encoding: gzip,deflate
Accept-Charset: gb2312,utf-8;q=0.7,*;q=0.7
Keep-Alive: 300
Connection: keep-alive
我们在服务器端把收到的数据打印出来，可以看到浏览器发过来的就是这个东西。当然，也可以用ethereal等抓包工具来抓获这些报文。关于报文里写的是什么意思，网上有很多资料的，GOOGLE一下就有了。我们只看第一行。
GET表示是要从服务器获取文件，/index.html是文件的路径，这个路径是相对于服务器端程序所在文件夹的路径。如我的服务器端程序放在/home/mio/program/webserver1707/里面，那这个index.html在服务器上的绝对路径就是/home/mio/program/webserver1707/index.html。如果报文里是GET /admin/login.html HTTP/1.1的话,那么login.html文件在服务器端的路径是/home/mio/program/webserver1707/admin/login.html.HTTP/1.1表示的是HTTP协议的版本是1.1.
服务器端程序运行后，一直监听8848端品（0-1023的端口由IANA统一分配和控制的，不要用，最好选大一些的端口号。我原来用了个1234,用不了，还是选大一点好，可以用5460之类的啊～：） ），当监听到客户端发来的请求后，就与客户端建立链接，接收客户端发过来的请求报文。我们如果把这些报文打出来，就可以看到就是与上面请求报文类似的东西了。
下面我们要根据所接受的到的请求报文（GET /index.html HTTP/1.1）来决定放给客户端（即浏览器）什么东西。这里我们看到浏览器要的是index.html这样一个html文本，我们就在相应路径（/home/mio/program/webserver1707/index.html）找到这个文件，不过不要急着发给客户端，我们要先告诉客户端，发过去的是一个html文件，让浏览器做好相应的准备。怎么让浏览器知道呢？我们还是用报文，这个报文叫响应报文。报文由状态行、首部行、实体主体三部分组成。状态行只有一行，它和首部行、首部行的每行之间是没有空行的，但是首部行与实体主体之间有一个空行，表明从这个空行开始，就是你浏览器要的数据了。下面是一个用ethereal抓到的响应报文：
HTTP/1.1 200 OK
Cache-Control: private
Content-Type: text/html; charset=UTF-8
Content-Encoding: gzip
Server: GWS/2.1
Content-Length: 1851
Date: Sat, 14 Oct 2006 11:33:39 GMT
<html><head><meta http-equiv="content-type" content="text/html; charset=UTF-8"><title>Google</title><style><!--
body,td,a,p,.h{font-family:arial,sans-serif}
.h{font-size:20px}
.q{color:#00c}
--></style>
<script>
<!--
function sf(){document.f.q.focus();}
function clk(url,oi,cad,ct,cd,sg){if(document.images){var e = window.encodeURIComponent ? encodeURIComponent : escape;var u="";var oi_param="";var cad_param="";if (url) u="&url="+e(url.replace(/#.*/,"")).replace(/\+/g,"%2B");if (oi) oi_param="&oi="+e(oi);if (cad) cad_param="&cad="+e(cad);new Image().src="/url?sa=T"+oi_param+cad_param+"&ct="+e(ct)+"&cd="+e(cd)+u+"&ei=E8swRYIOkpKwAvzZ8JkB"+sg;}return true;}
// -->
</script>
</head><body bgcolor=#ffffff text=#000000 link=#0000cc vlink=#551a8b alink=#ff0000 onLoad=sf() topmargin=3 marginheight=3><center><div align=right nowrap style="padding-bottom:4px" width=100%><font size=-1><b>manioster@gmail.com</b> | <a href="/url?sa=p&pref=ig&pval=3&q=http://www.google.com/ig%3Fhl%3Dzh-CN&sig=__1eXNMn0jGllmJ57x74DzjVvy6Vk=" onmousedown="return clk('/url?sa=p&pref=ig&pval=3&q=http://www.google.com/ig%3Fhl%3Dzh-CN&sig=__1eXNMn0jGllmJ57x74DzjVvy6Vk=','promos','hppphou:zh-cn_all','pro','1','&sig2=zclmOmtQiZPPuTCMWUJMZA')">个性化主页</a> | <a href="https://www.google.com/accounts/ManageAccount">我的帐户</a> | <a href="http://www.google.com/accounts/Logout?continue=http://www.google.com/intl/zh-CN/">退出</a></font></div><img src="/intl/zh-CN_ALL/images/logo.gif" width=286 height=110 alt="Google"><br><br>
<form action=/search name=f><script><!--
function qs(el) {if (window.RegExp && window.encodeURIComponent) {var ue=el.href;var qe=encodeURIComponent(document.f.q.value);if(ue.indexOf("q=")!=-1){el.href=ue.replace(new RegExp("q=[^&$]*"),"q="+qe);}else{el.href=ue+"&q="+qe;}}return 1;}
// -->
..........
第一个空行上面的就是“说明”了，下面是html代码。有了说明，浏览器就知道这是什么了，拿到这段数据后，就把这些html标签解释成各种各样的元素，在浏览器上有序地显示出来。浏览器还蛮聪明的，当看到<img src=..>标签，那就会又自己发一个请求报文给服务器，要求得到一个图像文件，请求报文就像：
....
这样，服务器端就找到这个.jpg图像，加上"说明"之后发给浏览器，浏览器收到后就显示在对应的位置上。遇到包含css、js...的标签也一样。
如此重复，一个完整的web就会呈现在我们眼前了。
服务器端代码：
mymultiwebserver.c
system:redhat linux Fedora Core 5
enviroment:g++
compile command:g++ -g -o mymultiwebserver -lpthread
date:10/15/2006
By Manio
**************************************************************** */
#include < stdlib.h >
#include < sys / types.h >
#include < sys / socket.h >
#include < sys / stat.h >
#include < netinet / in .h >
#include < unistd.h >
#include < pthread.h >
#include < stdio.h >
#include < string .h >
#include < arpa / inet.h >
#define PORT 8848
#define BACKLOG 5
#define MAXDATASIZE 1000
#define DEBUG 1
void process_cli( int connectfd, sockaddr_in client);
int sendobj( int connectfd, char * serverfilepath);
int IsDIR( char * fpath);
int fileordirExist( char * fpath);
char * getextname( char * );
int writehead(FILE * cfp, char * extname);
void * start_routine( void * arg);
void msg404( int connectfd);
struct ARG {
int connfd;
sockaddr_in client;
};
main()
{
int listenfd, connectfd;
pthread_t thread; // id of thread
ARG * arg; // pass this var to the thread
struct sockaddr_in server; // server's address info
struct sockaddr_in client; // client's
int sin_size;
// create tcp socket
#ifdef DEBUG
printf( " socket.... " );
#endif
if ((listenfd = socket(AF_INET, SOCK_STREAM, 0 )) == - 1 ) {
perror( " creating socket failed. " );
exit( 1 );
}
int opt = SO_REUSEADDR;
setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, & opt, sizeof (opt));
bzero( & server, sizeof (server));
server.sin_family = AF_INET;
server.sin_port = htons(PORT);
server.sin_addr.s_addr = htonl(INADDR_ANY);
printf( " bind.... " );
if (bind(listenfd,( struct sockaddr * ) & server, sizeof ( struct sockaddr)) == - 1 ) {
perror( " bind error. " );
exit( 1 );
}
printf( " listen.... " );
if (listen(listenfd,BACKLOG) == - 1 ) {
perror( " listen() error " );
exit( 1 );
}
sin_size = sizeof ( struct sockaddr_in);
while ( 1 )
{
// accept() using main thread
printf( " accepting.... " );
if ((connectfd = accept(listenfd,
( struct sockaddr * ) & client,
(socklen_t * ) & sin_size)) == - 1 ) {
printf( " accept() error " );
}
arg = new ARG;
arg -> connfd = connectfd;
memcpy(( void * ) & arg -> client, & client, sizeof (client));
// invoke start_routine to handle this thread
#ifdef DEBUG
printf( " thread_creating.... " );
#endif
if (pthread_create( & thread, NULL, start_routine, ( void * )arg)){
perror( " pthread_create() error " );
exit( 1 );
}
}
close(listenfd);
}
// handle the request of the client
void process_cli( int connectfd, sockaddr_in client)
{
int num;
// char recvbuf[MAXDATASIZE], sendbuf[MAXDATASIZE], cli_name[MAXDATASIZE];
char requestline[MAXDATASIZE], filepath[MAXDATASIZE], cmd[MAXDATASIZE],extname[MAXDATASIZE];
int c;
FILE * fp;
FILE * cfp;
fp = fdopen(connectfd, " r " );
#ifdef DEBUG
printf( " the host is:%s " ,inet_ntoa(client.sin_addr) );
#endif
fgets(requestline,MAXDATASIZE,fp);
#ifdef DEBUG
printf( " THE REQUEST IS :%s " ,requestline);
#endif
strcpy(filepath, " ./ " );
sscanf(requestline, " %s%s " ,cmd,filepath + 2 );
strcpy(extname, getextname(filepath));
#ifdef DEBUG
printf( " cmd:%s filepath:%s extname:%s " ,cmd,filepath,extname);
printf( " string comparing :::::::::::::start::::::::::::::: " );
#endif
if (strcmp(cmd, " GET " ) == 0 ){
// the command is get
#ifdef DEBUG
printf( " cmd(%s)==GET " ,cmd);
#endif
// is this a file or dir or notexist?
if (fileordirExist(filepath)){
// is a file or dir or none
// is this a dir
if (IsDIR(filepath)){
// is a dir
#ifdef DEBUG
printf( " %s is a DIR " ,filepath);
#endif
if ( fileordirExist( strcat(filepath, " index.htm " ) )){
sendobj(connectfd, " index.htm " );
} else if (fileordirExist(strcat(filepath, " index.html " ))){
sendobj(connectfd, " index.htm " );
} else {
msg404(connectfd);
}
} else {
// is a file
#ifdef DEBUG
printf( " %s is a file " ,filepath);
#endif
sendobj(connectfd,filepath);
}
} else {
#ifdef DEBUG
printf( " 404 " );
#endif
msg404(connectfd);
}
} else {
#ifdef DEBUG
printf( " cmd(%s)!=GET " ,cmd);
#endif
}
#ifdef DEBUG
printf( " :::::::::::::end::::::::::::::: " );
#endif
close(connectfd);
}
// send the 404 error message to the client
void msg404( int connectfd)
{
char * msg;
msg = " HTTP/1.0 404 Not Found Content-Type: text/plain 404 not found by Manio " ;
send(connectfd,msg,strlen(msg), 0 );
}
// is the filepath a file or directory
int fileordirExist( char * fpath)
{
struct stat filestat;
return ( stat(fpath, & filestat) != - 1 );
}
// is the filepath a directory
int IsDIR( char * fpath)
{
#ifdef DEBUG
printf( " IN IsDIR " );
#endif
struct stat filestat;
return ( stat(fpath, & filestat) != - 1 && S_ISDIR(filestat.st_mode));
}
// send the data of the file which the client want
int sendobj( int connectfd, char * serverfilepath)
{
FILE * sfp, * cfp;
int c;
sfp = fopen(serverfilepath, " r " );
cfp = fdopen(connectfd, " w " );
writehead(cfp,getextname(serverfilepath));
while ( (c = getc(sfp)) != EOF)putc(c,cfp);
fflush(cfp);
return 0 ;
}
// write the packet header to the client
int writehead(FILE * cfp, char * extname)
{
#ifdef DEBUG
printf( " INWRITEHEAD:::::::extname is %s::::::: " ,extname);
#endif
char * content = " text/plain " ;
if ( strcmp(extname, " html " ) == 0 || strcmp(extname, " htm " ) == 0 )
content = " text/html " ;
else if ( strcmp(extname, " css " ) == 0 )
content = " text/css " ;
else if ( strcmp(extname, " gif " ) == 0 )
content = " image/gif " ;
else if ( strcmp(extname, " jpeg " ) == 0 || strcmp(extname, " jpg " ) == 0 )
content = " image/jpeg " ;
else if ( strcmp(extname, " png " ) == 0 )
content = " image/png " ;
#ifdef DEBUG
printf( " HTTP/1.1 200 OK " );
printf( " Content-Type: %s " ,content);
#endif
fprintf(cfp, " HTTP/1.1 200 OK " );
fprintf(cfp, " Content-Type: %s " ,content);
return 0 ;
}
// get the extent name of the file
char * getextname( char * filepath)
{
char * p;
if (( p = strrchr(filepath, ' . ' )) != NULL)
return p + 1 ;
return NULL;
}
// invoked by pthread_create
void * start_routine( void * arg)
{
ARG * info;
info = (ARG * )arg;
// handle client's requirement
process_cli(info -> connfd, info -> client);
delete arg;
pthread_exit(NULL);
}
运行方法：
在fc5中打开控制台，按下面的方法进行
[root@localhost webserver1707]# ls
admin header img index.htm~
chinaunix.html header~ index.htm mymultiwebserver.c
[root@localhost webserver1707]# g++ -g -o mymultiwebserver mymultiwebserver.c -lpthread
mymultiwebserver.c: In function 鈥榲oid* start_routine(void*)鈥?
mymultiwebserver.c:253: 璀﹀憡锛氬垹闄?鈥榲oid*鈥?鏈畾涔?[root@localhost webserver1707]# ./mymultiwebserver socket....
bind....
listen....
accepting....
thread_creating....accepting....
the host is:127.0.0.1
THE REQUEST IS :GET / HTTP/1.1
cmd:GET
filepath:.//
extname://
string comparing
:::::::::::::start:::::::::::::::
cmd(GET)==GET
IN IsDIR
.// is a DIR
INWRITEHEAD:::::::extname is htm:::::::
HTTP/1.1 200 OK
Content-Type: text/html
thread_creating....accepting....
:::::::::::::end:::::::::::::::
thread_creating....accepting....
the host is:127.0.0.1
THE REQUEST IS :GET /img/sb.jpg HTTP/1.1
cmd:GET
filepath:.//img/sb.jpg
extname:jpg
string comparing
:::::::::::::start:::::::::::::::
cmd(GET)==GET
IN IsDIR
.//img/sb.jpg is a fileINWRITEHEAD:::::::extname is jpg:::::::
HTTP/1.1 200 OK
Content-Type: image/jpeg
:::::::::::::end:::::::::::::::
the host is:127.0.0.1
THE REQUEST IS :GET /img/gcc.png HTTP/1.1
cmd:GET
filepath:.//img/gcc.png
extname:png
string comparing
:::::::::::::start:::::::::::::::
cmd(GET)==GET
IN IsDIR
.//img/gcc.png is a fileINWRITEHEAD:::::::extname is png:::::::
HTTP/1.1 200 OK
Content-Type: image/png
:::::::::::::end:::::::::::::::
放一个index.htm文件在此程序所在的文件夹，打开浏览器，在地址栏输入http://127.0.0.1:8848/，就可以看到网页了～
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