c - 非阻塞 TCP 接受器不从套接字读取

Question

我有下面的代码实现了一个非阻塞 TCP 接受器。客户端能够毫无问题地连接并且写入似乎也在发生，但是接受器不会从套接字中读取任何内容并且对 read() 的调用无限期地阻塞。我是否对接受器使用了错误的设置？

亲切的问候AFG

int main(){
    create_programming_socket();
    poll_programming_connect(); 
    while(1){
        poll_programming_read();
    }    
}


int create_programming_socket(){
   int cnt = 0;
   p_listen_socket = socket( AF_INET, SOCK_STREAM, 0 );
   if( p_listen_socket < 0 ){
       return 1;
   }      

   int flags = fcntl( p_listen_socket, F_GETFL, 0 );
   if( fcntl( p_listen_socket, F_SETFL, flags | O_NONBLOCK ) == -1 ){
       return 1;
   }

   bzero( (char*)&p_serv_addr, sizeof(p_serv_addr) );     

   p_serv_addr.sin_family = AF_INET;
   p_serv_addr.sin_addr.s_addr = INADDR_ANY;
   p_serv_addr.sin_port = htons( p_port );    

   if( bind( p_listen_socket, (struct sockaddr*)&p_serv_addr
   , sizeof(p_serv_addr) ) < 0 ) {
       return 1;
   }
   listen( p_listen_socket, 5 );
   return 0;
}


int poll_programming_connect(){
   int retval = 0;   
   static socklen_t p_clilen = sizeof(p_cli_addr);   
   int res = accept( p_listen_socket, (struct sockaddr*)&p_cli_addr, &p_clilen );
   if( res > 0 ){
       p_conn_socket = res;
       int flags = fcntl( p_conn_socket, F_GETFL, 0 );
       if( fcntl( p_conn_socket, F_SETFL, flags | O_NONBLOCK ) == -1 ){   
           retval = 1;
       }else{
           p_connected = true;       
       }
    }else if( res == -1 && ( errno == EWOULDBLOCK || errno == EAGAIN ) ) {
    //printf( "poll_sock(): accept(c_listen_socket) would block\n");    
    }else{
       retval = 1;
   }
   return retval;
  }

  int poll_programming_read(){
   int retval = 0;
   bzero( p_buffer, 256 );   
   int numbytes = read( p_conn_socket, p_buffer, 255 );
   if( numbytes > 0 ) {
       fprintf( stderr, "poll_sock(): read() read %d bytes\n", numbytes );
       int fred;
        int i;
   } else if( numbytes == -1 && ( errno == EWOULDBLOCK || errno == EAGAIN ) ) {
    //printf( "poll_sock(): read() would block\n");
   } else {
       close( p_conn_socket );
       p_connected = false;
       retval = 1;
   }
   return retval;
 }

Answer 1

对 poll_programming_connect 的调用在您的 while 循环之外 - 因此它很可能不接受连接(因 EWOULDBLOCK 而失败)。因此，您没有可读取的有效套接字。

在调用 poll_programming_read 之前，您需要等到建立连接。