Linux网络编程--使用epoll模型同时处理tcp和udp服务

在实际工作中，服务器需要同时监听和处理tcp和udp的套接字，同时监听N多的端口。根据bind系统调用来讲，一个socket只能监听一个端口，因此要创建多个socket并绑定到各个端口上。当然同一个端口可以同时绑定tcp和udp的socket，但是要创建两个socket，一个是tcp的一个是udp的。

下面我们就写一个可以同时处理tcp和udp服务的回射服务器。

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <assert.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <fcntl.h>
#include <stdlib.h>
#include <sys/epoll.h>
#include <pthread.h>

#define MAX_EVENT_NUMBER 1024
#define TCP_BUFFER_SIZE 512
#define UDP_BUFFER_SIZE 1024

int setnonblocking( int fd )
{
int old_option = fcntl( fd, F_GETFL );
int new_option = old_option | O_NONBLOCK;
fcntl( fd, F_SETFL, new_option );
return old_option;
}

void addfd( int epollfd, int fd )
{
epoll_event event;
event.data.fd = fd;
//event.events = EPOLLIN | EPOLLET;
event.events = EPOLLIN;//可读事件，默认为LT模式，事件一般被触发多次
epoll_ctl( epollfd, EPOLL_CTL_ADD, fd, &event );
setnonblocking( fd );
}

int main( int argc, char* argv[] )
{
if( argc <= 2 )
{
printf( "usage: %s ip_address port_number\n", basename( argv[0] ) );
return 1;
}
const char* ip = argv[1];
int port = atoi( argv[2] );

int ret = 0;
//创建tcp套接字，并绑定 、监听
struct sockaddr_in address;
bzero( &address, sizeof( address ) );
address.sin_family = AF_INET;
inet_pton( AF_INET, ip, &address.sin_addr );
address.sin_port = htons( port );

int listenfd = socket( PF_INET, SOCK_STREAM, 0 );
assert( listenfd >= 0 );

ret = bind( listenfd, ( struct sockaddr* )&address, sizeof( address ) );
assert( ret != -1 );

ret = listen( listenfd, 5 );
assert( ret != -1 );
//创建udp套接字，并绑定
bzero( &address, sizeof( address ) );
address.sin_family = AF_INET;
inet_pton( AF_INET, ip, &address.sin_addr );
address.sin_port = htons( port );
int udpfd = socket( PF_INET, SOCK_DGRAM, 0 );
assert( udpfd >= 0 );

ret = bind( udpfd, ( struct sockaddr* )&address, sizeof( address ) );
assert( ret != -1 );

epoll_event events[ MAX_EVENT_NUMBER ];
int epollfd = epoll_create( 5 );
assert( epollfd != -1 );
//注册tcp和udp套接字的可读事件
addfd( epollfd, listenfd );
addfd( epollfd, udpfd );

while( 1 )
{
int number = epoll_wait( epollfd, events, MAX_EVENT_NUMBER, -1 );
if ( number < 0 )
{
printf( "epoll failure\n" );
break;
}

for ( int i = 0; i < number; i++ )
{
int sockfd = events[i].data.fd;
//tcp有新的可读事件，也即接受到了新的连接
if ( sockfd == listenfd )
{
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof( client_address );
int connfd = accept( listenfd, ( struct sockaddr* )&client_address, &client_addrlength );
//将新的连接套接字也注册可读事件
addfd( epollfd, connfd );
}
//udp套接字事件处理
else if ( sockfd == udpfd )
{
char buf[ UDP_BUFFER_SIZE ];
memset( buf, '\0', UDP_BUFFER_SIZE );
struct sockaddr_in client_address;
socklen_t client_addrlength = sizeof( client_address );

ret = recvfrom( udpfd, buf, UDP_BUFFER_SIZE-1, 0, ( struct sockaddr* )&client_address, &client_addrlength );
if( ret > 0 )
{
sendto( udpfd, buf, UDP_BUFFER_SIZE-1, 0, ( struct sockaddr* )&client_address, client_addrlength
4000
);
}
}
//注册的socket发生可读事件
else if ( events[i].events & EPOLLIN )
{
char buf[ TCP_BUFFER_SIZE ];
while( 1 )
{
memset( buf, '\0', TCP_BUFFER_SIZE );
ret = recv( sockfd, buf, TCP_BUFFER_SIZE-1, 0 );
if( ret < 0 )
{
//数据接受完毕之后进入下一次可读事件
if( ( errno == EAGAIN ) || ( errno == EWOULDBLOCK ) )
{
break;
}
close( sockfd );
break;
}
//服务端已经断开连接，所以断开客户端连接
else if( ret == 0 )
{
close( sockfd );
}
else
{
send( sockfd, buf, ret, 0 );
}
}
}
else
{
printf( "something else happened \n" );
}
}
}

close( listenfd );
return 0;
}

转自：http://blog.csdn.net/hnlyyk/article/details/50955053