AVMediaServiceUtils::makePortPair-优快云博客

本文链接：https://blog.youkuaiyun.com/u011294619/article/details/61922396

本文介绍了一个用于创建RTP与RTCP端口对的实用函数，该函数利用ARTPConnection::MakePortPair实现，通过随机选择端口号并在指定的地址族下创建UDP套接字，为实时音视频传输提供了必要的网络基础设施。

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void AVMediaServiceUtils::makePortPair(int *rtpSocket, int *rtcpSocket, unsigned *rtpPort,
        bool /*isIPV6*/) {
    //通过调用ARTPConnection::MakePortPair来完成rtp套接口和rtcp套接口的创建
    //端口号由rtpPort值传回
    //rtp套接口描述符由rtpSocket传回
    //rtcp套接口由rtcpSocket传回
    //isIPV6暂时未被使用
    return ARTPConnection::MakePortPair(rtpSocket, rtcpSocket, rtpPort);
}

// static
void ARTPConnection::MakePortPair(
        int *rtpSocket, int *rtcpSocket, unsigned *rtpPort) {
    *rtpSocket = socket(AF_INET, SOCK_DGRAM, 0);
    CHECK_GE(*rtpSocket, 0);

    bumpSocketBufferSize(*rtpSocket);

    *rtcpSocket = socket(AF_INET, SOCK_DGRAM, 0);
    CHECK_GE(*rtcpSocket, 0);

    bumpSocketBufferSize(*rtcpSocket);

    /* rand() * 1000 may overflow int type, use long long */
    unsigned start = (unsigned)((rand()* 1000ll)/RAND_MAX) + 15550;
    start &= ~1;

    for (unsigned port = start; port < 65536; port += 2) {
        struct sockaddr_in addr;
        memset(addr.sin_zero, 0, sizeof(addr.sin_zero));
        addr.sin_family = AF_INET;
        addr.sin_addr.s_addr = htonl(INADDR_ANY);
        addr.sin_port = htons(port);

        if (bind(*rtpSocket,
                 (const struct sockaddr *)&addr, sizeof(addr)) < 0) {
            continue;
        }

        addr.sin_port = htons(port + 1);

        if (bind(*rtcpSocket,
                 (const struct sockaddr *)&addr, sizeof(addr)) == 0) {
            *rtpPort = port;
            return;
        }
    }

    TRESPASS();
}