无法将套接字绑定到地址

Question

我正在尝试编写一些客户端代码，以将UDP数据包发送到具有特定IP地址的另一台计算机。当IP地址设置为home时，它工作正常。我可以使用Wireshark查看发送的数据包。当我放入服务器的IP时，我没有看到任何数据包。经过进一步调查，我发现尝试绑定到套接字时遇到了10049错误。我不太明白为什么我无法绑定到网络上另一台计算机的IP。

    string m_port = "2033";             //  port that the plugin is talking to
    string m_hostIP = "192.168.2.27";           //  IP address that the plugin is talking to

    //  start Windows Sockets
    if ((error = WSAStartup(version, &data)) != NO_ERROR)
    {
        logError("Error: WSAStartup failed with error: ", error);
        return;
    }
    // check if version 2.2 of Winsock is supported
    if (LOBYTE(data.wVersion) != 2 || HIBYTE(data.wVersion) != 2)
    {
        logError("Error: System could not support WinSock 2.2.", 0);
        // clean up Winsock
        if (WSACleanup() == SOCKET_ERROR)
        {
            logError("Error: Winsock cleanup error: ", WSAGetLastError());
        }
        return;
    }

    //  create a datagram socket using IPv4 and UDP protocol
    if ((m_socket = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) == INVALID_SOCKET)
    {
        logError("Error: Socket creation failed with error: ", WSAGetLastError());
        //  clean up Winsock
        if (WSACleanup() == SOCKET_ERROR)
        {
            logError("Error: Winsock cleanup error: ", WSAGetLastError());
        }
        return;
    }

    int iSetOption = 1;
    if (setsockopt(m_socket, SOL_SOCKET, SO_REUSEADDR, (char*)&iSetOption, sizeof(iSetOption)) == SOCKET_ERROR)
    {
        logError("Error: Set Socket Options failed with error: ", WSAGetLastError());

        //  close the socket
        if (closesocket(m_socket) == SOCKET_ERROR)
        {
            logError("Error: Unable to close socket: ", WSAGetLastError());
        }
        //  clean up Winsock
        if (WSACleanup() == SOCKET_ERROR)
        {
            logError("Error: Winsock cleanup error: ", WSAGetLastError());
        }

        m_socket = INVALID_SOCKET;
        return;
    }

    struct sockaddr_in server_addr;             //  server address description struct
    int server_addr_len = sizeof(server_addr);  //  size of server address struct
    int bytesSent = 0;

    memset((char *)&server_addr, 0, server_addr_len);           //  clear the address struct
    server_addr.sin_family = AF_INET;                           //  IPv4 address type
    server_addr.sin_port = htons((unsigned short)stoul(m_port));    //  port used by the simulator to send the data
    server_addr.sin_addr.s_addr = inet_addr(m_hostIP.c_str());          //  any server IP address will do

    //  bind the socket to the address struct
    if (::bind(m_socket, (struct sockaddr *) &server_addr, server_addr_len) == SOCKET_ERROR)
    {
        logError("Error: unable to bind the socket: ", WSAGetLastError());
        //  close the socket
        if (closesocket(m_socket) == SOCKET_ERROR)
        {
            logError("Error: Unable to close socket: ", WSAGetLastError());
        }
        // clean up Winsock
        if (WSACleanup() == SOCKET_ERROR)
        {
            logError("Error: Winsock cleanup error: ", WSAGetLastError());
        }

        m_socket = INVALID_SOCKET;
        return;
    }

Answer 1

您绑定套接字以选择从哪个本地端点（地址+端口）发送数据。

服务器可能具有将您连接到Internet的多个网卡，或者您可能具有多个网络-通过绑定，您可以选择从哪个网卡（或实际的网卡）中发送数据。

通常，PC仅具有一些可行的地址（本地主机和网络地址），但是您也可以指定端口。端口可用于过滤不需要的数据包，这在您要创建多个套接字时很有用。

另一个操作称为connect-选择向哪个远程端点发送数据。我不记得确切的细节如何在winsocket / udp上工作。可能没有必要，您只需发送数据，然后指定每次发送的位置即可。