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 1024int 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 );                }            }            //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