c++ - 如何在 C++ 中使用套接字 (UDP) 在 LAN 上查找服务器

Question

各位程序员大家好!我正在用 C++ 编写一个程序，该程序应该允许使用 Windows 套接字通过 LAN 在两台计算机之间进行实时数据传输。由于数据应该尽可能快地传输，我使用 UDP(这是一个游戏，因此只有最新的数据是相关的)。现在，因为我在单台机器上测试过它，所以我使用以下代码将服务器 IP 分配给客户端

SOCKADDR_IN server_address;
server_address.sin_family = AF_INET;
server_address.sin_port = htons(PORT);
server_address.sin_addr.S_un.S_un_b.s_b1 = 127;
server_address.sin_addr.S_un.S_un_b.s_b2 = 0;
server_address.sin_addr.S_un.S_un_b.s_b3 = 0;
server_address.sin_addr.S_un.S_un_b.s_b4 = 1;

现在，我需要它在 LAN 中运行，其中服务器和客户端的确切地址可能是未知的。在这种情况下如何连接？如果我广播到 255.255.255.255 就够了吗？或者，也许还有另一种方式来握手 2 台计算机？

Answer 1

好的，我完成了我的项目，所以我将借此机会展示我用于查找服务器的代码。如建议的那样，它基于客户端广播并发回数据报，将服务器的 IP 提供给客户端，稍后用于提供定向通信。

服务器:

bool handshakeS()
{
    SOCKET sockhs;
    sockhs = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

    char broadcast = '1';
    if (setsockopt(sockhs, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast)) < 0)
    {
        closesocket(sockhs);
        return false;
    }

    struct sockaddr_in Recv_addr;
    struct sockaddr_in Sender_addr;

    int len = sizeof(struct sockaddr_in);

    char recvbuff[1];
    int recvbufflen = 1;
    char sendMSG[] = "";

    Recv_addr.sin_family = AF_INET;
    Recv_addr.sin_port = htons(PORTHS);
    Recv_addr.sin_addr.s_addr = INADDR_ANY;

    if (bind(sockhs, (sockaddr*)&Recv_addr, sizeof(Recv_addr)) < 0)
    {
        closesocket(sockhs);
        return false;
    }
    recvfrom(sockhs, recvbuff, recvbufflen, 0, (sockaddr*)&Sender_addr, &len);

    if (sendto(sockhs, sendMSG, strlen(sendMSG) + 1, 0, (sockaddr*)&Sender_addr, sizeof(Sender_addr)) < 0)
    {
        closesocket(sockhs);
        return false;
    }
    return true;
    closesocket(sockhs);
}

客户:

bool handshakeC(int& ip1temp, int& ip2temp, int& ip3temp, int& ip4temp)
{
    SOCKET sockhs;
    sockhs = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);

    char broadcast = '1';
    if (setsockopt(sockhs, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast)) < 0)
    {
        closesocket(sockhs);
        return false;
    }

    struct sockaddr_in Recv_addr;
    struct sockaddr_in Sender_addr;

    int len = sizeof(struct sockaddr_in);

    char sendMSG[] = ""; //may be used for authorization
    char recvbuff[1] = "";
    int recvbufflen = 1;

    Recv_addr.sin_family = AF_INET;
    Recv_addr.sin_port = htons(PORTHS);
    Recv_addr.sin_addr.s_addr = INADDR_BROADCAST;

    sendto(sockhs, sendMSG, strlen(sendMSG) + 1, 0, (sockaddr*)&Recv_addr, sizeof(Recv_addr));
    recvfrom(sockhs, recvbuff, recvbufflen, 0, (sockaddr*)&Recv_addr, &len);

    ip1temp = Recv_addr.sin_addr.S_un.S_un_b.s_b1;
    ip2temp = Recv_addr.sin_addr.S_un.S_un_b.s_b2;
    ip3temp = Recv_addr.sin_addr.S_un.S_un_b.s_b3;
    ip4temp = Recv_addr.sin_addr.S_un.S_un_b.s_b4;
    closesocket(sockhs);
    return true;
}