Question

我正在MFC中实现TFTP客户端应用程序。以下是两个功能：

1）连接服务器功能..

int TFTPClient::connectToServer() {

  cout << "Connecting to " << server_ip << " on port " << server_port <<  endl;

socket_descriptor = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

if (socket_descriptor == -1) {

    throw new ETFTPSocketCreate;

}

client_address.sin_family = AF_INET;
client_address.sin_port = htons(server_port);   //- taip pat turi buti ir serveryje!
client_address.sin_addr.s_addr = inet_addr(this->server_ip);

#ifdef WIN32
    //memset(client_address.sin_zero, 0, sizeof(client_address.sinzero);
    //- suvienodinam SOCKADDR_IN ir SOCKADDR strukturu dydzius
#endif

connection = connect(socket_descriptor, (const struct sockaddr  *)&client_address, sizeof(client_address));

if (connection != 0) {

    cout << "Unable to connect to an address\n";
    return -1;

}

DEBUGMSG("Successfully connected");

AfxMessageBox("Successfully connected");

return 1;

}

2）等待回应...

int TFTPClient::waitForPacket(TFTP_Packet* packet, int timeout_ms) {

packet->clear();

fd_set fd_reader;         
timeval connection_timer; 

connection_timer.tv_sec = timeout_ms / 1000; // = 2
connection_timer.tv_usec = 0; 

FD_ZERO(&fd_reader);

FD_SET(socket_descriptor, &fd_reader);

int select_ready = select(socket_descriptor + 1, &fd_reader, NULL, NULL, &connection_timer);

if (select_ready == -1) {

#ifdef WIN32
    cout << "Error in select(), no: " << WSAGetLastError() << endl;
#else
    cout << "Error in select(): " << endl;
#endif

return TFTP_CLIENT_ERROR_SELECT;

} else if (select_ready == 0) {

    DEBUGMSG("Timeout");

    return TFTP_CLIENT_ERROR_TIMEOUT;

}



int receive_status;

receive_status = recv(socket_descriptor, (char*)packet->getData(), TFTP_PACKET_MAX_SIZE, 0);

if (receive_status == 0) {
    cout << "Connection was closed by server\n";
    return TFTP_CLIENT_ERROR_CONNECTION_CLOSED;
}

if (receive_status == SOCKET_ERROR) {
    DEBUGMSG("recv() error in waitForPackage()");
    return TFTP_CLIENT_ERROR_RECEIVE;
}



packet->setSize(receive_status);

return TFTP_CLIENT_ERROR_NO_ERROR;

}

每次运行应用程序时，函数2中的select函数返回0，表示超时。我的问题：有没有其他方法可以在不使用select（）的情况下实现整个函数？或者在我打电话给recv之前这个功能是否必要？我不知道为什么会有超时，我知道我只需要在发送下一个数据包之前从服务器接收一个ack并循环直到文件完全传输。

Answer 1

如果您只想担心单个文件描述符，并且想要无限期等待，请不要打扰select。只需致电recv，这将阻止您获取数据。

winsock select（）函数返回0

1 个答案: