c - UDP 服务器收不到数据

Question

UDP 服务器没有收到UDP 客户端程序发送的数据。我觉得我在UDP 服务器程序中做错了。谢谢。

   send_client_message = malloc(message_size);
  recv_client_message = malloc(message_size);
  sockaddr_in_length = sizeof(struct sockaddr_in);

  /* Create a datagram socket.*/
  server_sock = socket(AF_INET,SOCK_DGRAM,0);
  if (server_sock == return_error)
  {
    printf("Error in opening a datagram socket\n");
    exit(0);
  }
  printf("Host sock = %d\n",server_sock);

  /* Bind a local name to the socket.*/
  server_sockaddr_in.sin_family      = AF_INET;
  server_sockaddr_in.sin_port        = 4999;
  server_sockaddr_in.sin_addr.s_addr = INADDR_ANY;
  rc = bind(server_sock,(struct sockaddr *)&server_sockaddr_in,
            sockaddr_in_length);
  if (rc == return_error)
  {
    printf("Error in binding - \n");
    (void)close(server_sock);
    exit(0);
  }

  /* Get the server information, and print its data out.*/
  rc = getsockname(server_sock,(struct sockaddr *)&server_sockaddr_in,
                   &sockaddr_in_length);
  if (rc != return_error)
  {
    printf("Server Information\n");
    printf("--------------------------------\n");
    printf("Server sock       - %d\n",server_sock);
    printf("Server IP address - %x\n",
                                  server_sockaddr_in.sin_addr.s_addr);
    printf("Server port #     - %d\n\n",
                                  server_sockaddr_in.sin_port);
  }

  optval = message_size;
  optlen = sizeof(optval);
  rc = setsockopt(server_sock,SOL_SOCKET,SO_SNDBUF,(char *)&optval,
                  optlen);
  if (rc == return_error)
  {
    //printf("Error in setsockopt - %d\n",sock_errno());
    printf("Error in setsockopt - \n");
    (void)close(server_sock);
    exit(0);
  }

  printf(".... Ready for clients ....\n");

  /* Loop forever */
  for (;;)
  {
    /* Monitor incoming buffers.   */
    rc = recvfrom(server_sock,recv_client_message,message_size,0,
                  (struct sockaddr *)&client_sockaddr_in,
                  &sockaddr_in_length);

    printf("Recieved packet from %s: %d\nData: %s\n\n", inet_ntoa(client_sockaddr_in.sin_addr), ntohs(client_sockaddr_in.sin_port), recv_client_message); 
   fflush(stdout);

    if (rc == return_error)
    {
      printf("Error in receiving message \n");
      break;
    }
   }  /* end of for(;;) */

  /* Return the socket back to the system and exit normally.  */
  rc = close(server_sock);
  if (rc == return_error)
  {
    printf("Error in closing the socket  \n");
    exit(0);
  }

  printf("Datagram server terminated\n");
  exit(0);
}


    for(i = 0; i < NPACK; i += 1) {
        printf("Sending packet %d\n", i);
        sprintf(buf, "This is packet %d\n", i);
        if(sendto(s, buf, BUFLEN, 0, (struct sockaddr *) &si_other, slen) == -1)
            diep("sendto()");
    }

    close(s);
    return 0;
}

Answer 1

server_sockaddr_in.sin_port        = 4999;

您可能想要 htons 那个 4999。