第九章 select用法初试-优快云博客

本文介绍了一个简单的TCP服务器实现，使用C语言并通过多个网络编程API进行搭建。该服务器能够接受客户端连接，显示客户端地址和端口，并能处理客户端发送的数据，区分普通数据与带外数据。

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#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>

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] );
	printf( "ip is %s and port is %d\n", ip, port );

	int ret = 0;
        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 );

	struct sockaddr_in client_address;
        socklen_t client_addrlength = sizeof( client_address );
	int connfd = accept( listenfd, ( struct sockaddr* )&client_address, &client_addrlength );
	if ( connfd < 0 )
	{
		printf( "errno is: %d\n", errno );
		close( listenfd );
	}

	char remote_addr[INET_ADDRSTRLEN];
	printf( "connected with ip: %s and port: %d\n", inet_ntop( AF_INET, &client_address.sin_addr, remote_addr, INET_ADDRSTRLEN ), ntohs( client_address.sin_port ) );
	//设置了文件描述符集:read_fds,read_exception_fds
	char buf[1024];
        fd_set read_fds;
        fd_set exception_fds;
		//初始化清空
        FD_ZERO( &read_fds );
        FD_ZERO( &exception_fds );

        int nReuseAddr = 1;
	setsockopt( connfd, SOL_SOCKET, SO_OOBINLINE, &nReuseAddr, sizeof( nReuseAddr ) );//设置socket文件描述符属性
	while( 1 )
	{
		memset( buf, '\0', sizeof( buf ) );
		FD_SET( connfd, &read_fds );//将连接socket文件描述符connfd加入到read_fds,exception_fds中
		FD_SET( connfd, &exception_fds );
		//select监听文件描述符集:read_fds,read_exception_fds上的事件
        	ret = select( connfd + 1, &read_fds, NULL, &exception_fds, NULL );//注意这里connfd+1
		printf( "select one\n" );
        	if ( ret < 0 )
        	{
                	printf( "selection failure\n" );
                	break;
        	}
	
        	if ( FD_ISSET( connfd, &read_fds ) )//connfd上发生读事件
		{
        		ret = recv( connfd, buf, sizeof( buf )-1, 0 );
			if( ret <= 0 )
			{
				break;
			}
			printf( "get %d bytes of normal data: %s\n", ret, buf );
		}
		else if( FD_ISSET( connfd, &exception_fds ) )//connfd上异常事件
        	{
        		ret = recv( connfd, buf, sizeof( buf )-1, MSG_OOB );//读取带外数据
			if( ret <= 0 )
			{
				break;
			}
			printf( "get %d bytes of oob data: %s\n", ret, buf );
        	}

	}

	close( connfd );
	close( listenfd );
	return 0;
}