我在选择中使用read()时遇到问题 [英] I have a question when i use read() in select

问题描述

你好，当我使用select()和read()时，我有一个问题.
关键代码是:

hello , i have a question, when i use select() and read().
the key codes is :

nready = select( maxfd + 1, server->fd_readset, 0, 0, timeout );
       if( nready > 0 )
               printf( "nready is %d\n", nready );

       char buf[100];
       int n ;
       if ( FD_ISSET( server->fd , server->fd_readset ) )    /* new client connection */
       {
               int s = (int)accept( server->fd, 0, 0 );
               if ( s == -1 )
               {
                       printf( " errno is %d\n", errno );
                       fprintf( stdout, "error is %s\n", strerror( errno ) );
               }
               printf( "s is %d\n", s );
               for ( j = 0; j < FD_SETSIZE; j++ )
               {
                       if ( client[j] < 0 )
                       {
                               if( s > 0 )
                                       client[j] = s;  /* save descriptor */
                               break;
                       }
                }
        
        if ( j == FD_SETSIZE )
        {
                printf( "too much clients!\n" );
        }
        FD_SET( s, server->fd_set );    /* add new descriptor to set */
        if( s > maxfd )
                maxfd = s;      /* for select */
        if( j > maxi )
                maxi = j;       /* max index in client[] array */
        if( --nready <= 0 )
                continue;
}
/*printf( "client[0] is %d\n", client[0] );*/
for( j = 0; j <= maxi; j++ )
{
        if( ( sockfd = client[j] ) < 0 )
                continue;
        if( FD_SET( sockfd, server->fd_readset ) )
        {
                if( ( n = read( sockfd, buf, 100) ) != 0 )
                {

问题是:我启动了服务器，但是我只允许一个客户端通过write()函数将消息发送到服务器.另一个客户端无法发送消息.
我已经用gdb调试了，我发现服务器在read()中阻塞了；服务器仍然读取第一个客户端.
我尝试使用alarm()来解决它，但是不起作用.当read()超时时，它仍然处于阻塞状态.
请告诉我为什么?谢谢.

the question is: i start up the server, but i just let only one client send messages to server by function of write(). the another client can''t send messages.
i have debug by gdb, i found the server is blocking in read(); the server still read the first client.
i try to use alarm() to solve it, but it don''t work.when the read() make the time out, it''s still blocking.
please tell me why? thank you.

推荐答案

服务器通过bind()连接到恰好一个客户端.如果要侦听另一个客户端，则必须绑定一个新套接字以连接传入的接受请求.因此，必须对每个绑定的套接字使用线程，因为请求是异步的.
问候.

The server is connected by the bind() to exactly one client. If you want to listen for another client you have to bind a new socket to connect on incoming accept requests. Therefore you have to use threads for each bound socket, because the requests are async.
Regards.

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