非阻塞socket引发的数据不完整

基于Socket的网络通讯方式，其I/O方式，由下面几种：

      •blocking I/O

      •nonblocking I/O

      •I/O multiplexing (select and poll)

非阻塞模式情况下，等待的资源未就位，呼叫函数就直接返回，查看系统errno，应该是WOULDBLOCK_ERR

{ if ((now = send(_peer, (char *)pos, size, 0)) == SOCKET_ERROR) {         int err = sock_error(); #if 1         if (err == WOULDBLOCK_ERR) {;             usleep(1);      // sleep, waiting; Try again, after OS sent packet in the send queue             continue;         } #else         if (err == WOULDBLOCK_ERR) {;             break;         //  Don’t wait, break; So the send data is truncated         } #endif         if (err == SHUTDOWN_ERR) {             throw DisconnectedException();         }         if (err == INTERRUPTED_ERR) {             continue;         }         THROW_ERR(ERROR_CODE_SEND_FAILED, "%s (%d)", sock_err_message(err), err);     }     size -= now;     pos += now; }