ThreadPool是一個執行緒池，具體實現就不貼了，隨便找個執行緒池實現就行，也可以戳這裡檢視程式完整程式碼。

P2PNode::P2PNode(const char *if_name)
{
    m_sock = socket(AF_INET, SOCK_DGRAM, 0);//IPV4  SOCK_DGRAM 資料報套接字（UDP協議）  
    if (m_sock < 0)
    {
        perror("socket\n");
        return ;
    }

    int val = 1;
    if (setsockopt(m_sock, SOL_SOCKET, SO_REUSEADDR, &val, sizeof
 
(val)) < 0)
    {
        perror("setsockopt");
    }

    struct timeval tv_out;
    tv_out.tv_sec = 10;//等待10秒
    tv_out.tv_usec = 0;
    if (setsockopt(m_sock, SOL_SOCKET, SO_RCVTIMEO, &tv_out, sizeof(tv_out)) < 0)
    {
        perror("setsockopt");
    }

    memset(&m_serverAddr, 0, sizeof
 
(m_serverAddr));
    m_serverAddr.sin_family = AF_INET;
    m_serverAddr.sin_port = htons(SERVERPORT);
    m_serverAddr.sin_addr.s_addr = inet_addr(SERVERIP);
    socklen_t serverLen = sizeof(m_serverAddr);

    memset(&m_localAddr, 0, sizeof(m_localAddr));
    m_localAddr.sin_family = AF_INET;
    m_localAddr.sin_port = htons(LOCALPORT);
    m_localAddr.sin_addr.s_addr = htonl(INADDR_ANY);
    if
 
 (bind(m_sock, (struct sockaddr*)&m_localAddr, sizeof(m_localAddr)) < 0)
    {
        perror("bind");
        close(m_sock);
        exit(2);
    }


    memset(&m_recvAddr, 0, sizeof(m_recvAddr));
    socklen_t recvLen = sizeof(m_recvAddr);

    NodeInfo sendNode, recvNode;
    memset(&sendNode, 0, sizeof(NodeInfo));
    memset(&recvNode, 0, sizeof(NodeInfo));
    sendNode.cmd = cmd_register;
    sendNode.node.recvPort = LOCALPORT;
    get_local_ip(if_name, sendNode.node.recvIp);

    while (1)
    {
        if (sendto(m_sock, &sendNode, sizeof(NodeInfo), 0, (struct sockaddr*)&m_serverAddr, serverLen) < 0)
        {
            perror("sendto");
            close(m_sock);
            exit(4);
        }

        memset(&m_recvAddr, 0, sizeof(m_recvAddr));
        memset(&recvNode, 0, sizeof(NodeInfo));
        if (recvfrom(m_sock, &recvNode, sizeof(NodeInfo), 0, (struct sockaddr*)&m_recvAddr, &recvLen) < 0)
        {
            if (errno == EINTR || errno == EAGAIN)
                continue;

            perror("recvfrom");
            close(m_sock);
            exit(2);
        }

        if (recvNode.cmd != cmd_register)
            continue;

        m_selfNode = recvNode.node;
        break;
    }

    while (1)
    {
        memset(&sendNode, 0, sizeof(NodeInfo));
        memset(&recvNode, 0, sizeof(NodeInfo));
        memset(&m_recvAddr, 0, sizeof(m_recvAddr));

        sendNode.cmd = cmd_getnode;
        sendNode.node = m_selfNode;
        if (sendto(m_sock, &sendNode, sizeof(NodeInfo), 0, (struct sockaddr*)&m_serverAddr, serverLen) < 0)
        {
            perror("sendto");
            close(m_sock);
            exit(4);
        }

        if (recvfrom(m_sock, &recvNode, sizeof(NodeInfo), 0, (struct sockaddr*)&m_recvAddr, &recvLen) < 0)
        {
            if (errno == EINTR || errno == EAGAIN)
                continue;

            perror("recvfrom");
            close(m_sock);
            exit(2);
        }

        if (recvNode.cmd != cmd_getnode)
            continue;

        m_otherNode = recvNode.node;
        break;
    }

    //查詢到的IP和接收到的IP如果不相同，則是內網環境
    //自己查詢到的IP和另一個節點查詢到的IP如果相同，則處於同一內網
    //同一內網的節點用內網傳輸資料，不在同一內網的節點只能用公網傳輸資料
    if (strcmp(m_selfNode.queryIp, m_selfNode.recvIp) &&
        !strcmp(m_selfNode.queryIp, m_otherNode.queryIp))
    {
        m_otherIP = m_otherNode.recvIp;
        m_otherPort = m_otherNode.recvPort;
    }
    else
    {
        m_otherIP = m_otherNode.queryIp;
        m_otherPort = m_otherNode.queryPort;
    }

    pthread_mutex_init(&m_mutexPack, NULL);
    pthread_mutex_init(&m_mutexResult, NULL);
}

P2PNode::~P2PNode()
{
    NodeInfo sendNode;
    memset(&sendNode, 0, sizeof(NodeInfo));

    socklen_t serverLen = sizeof(m_serverAddr);

    sendNode.cmd = cmd_unregister;
    sendNode.node = m_selfNode;
    if (sendto(m_sock, &sendNode, sizeof(NodeInfo), 0, (struct sockaddr*)&m_serverAddr, serverLen) < 0)
    {
        perror("sendto");
        close(m_sock);
        exit(4);
    }

    close(m_sock);

    pthread_mutex_destroy(&m_mutexPack);
    pthread_mutex_destroy(&m_mutexResult);
}

P2PNode* P2PNode::Instance(const char *if_name)
{
    static P2PNode node(if_name);
    return &node;
}

void P2PNode::Listen()
{
    if (pthread_create(&m_tid, NULL, threadFunc, this) != 0)
    {
        close(m_sock);
        exit(2);
    }
}
void *P2PNode::threadFunc(void *arg)
{
    P2PNode *p = (P2PNode*)arg;
    p->threadHandler();
    return NULL;
}

void P2PNode::threadHandler()
{
    sockaddr_in otherAddr;
    memset(&otherAddr, 0, sizeof(otherAddr));
    otherAddr.sin_family = AF_INET;
    otherAddr.sin_port = htons(m_otherPort);
    otherAddr.sin_addr.s_addr = inet_addr(m_otherIP);

    P2PMessage recvMess;
    P2PMessage sendMess;
    P2PResult result;

    socklen_t recvLen = sizeof(m_recvAddr);

    ThreadPool<P2PMessage, P2PNode> tp(1);
    tp.setTaskFunc(this, &P2PNode::combinationPackage);
    tp.start();

    while (1)
    {
        memset(&recvMess, 0, sizeof(P2PMessage));
        memset(&sendMess, 0, sizeof(P2PMessage));
        memset(&result, 0, sizeof(P2PResult));
        memset(&m_recvAddr, 0, sizeof(m_recvAddr));

        if (recvfrom(m_sock, &recvMess, sizeof(P2PMessage), 0, (struct sockaddr*)&m_recvAddr, &recvLen) < 0)
        {
            if (errno == EINTR || errno == EAGAIN)
                continue;

            perror("recvfrom");
            tp.stop();
            close(m_sock);
            exit(2);
        }

        if (recvMess.cmd == p2p_result)
        {
            memcpy(&result, recvMess.mess, recvMess.length);
            pthread_mutex_lock(&m_mutexResult);
            m_lstResult.push_back(result);
            pthread_mutex_unlock(&m_mutexResult);
            continue;
        }

        tp.addTask(recvMess);

        result.index = recvMess.index;
        memcpy(result.messHash, recvMess.messHash, sizeof(recvMess.messHash));
        sendMess.cmd = p2p_result;
        sendMess.length = sizeof(result);
        memcpy(sendMess.mess, &result, sendMess.length);
        if (sendto(m_sock, &sendMess, sizeof(sendMess), 0, (struct sockaddr*)&m_recvAddr, sizeof(m_recvAddr)) < 0)
        {
            perror("sendto");
            tp.stop();
            close(m_sock);
            exit(4);
        }
    }
    tp.stop();
}