C++实现多线程并发服务器（UDP案例）

Question

我使用 "Create-new-thread method" 来处理新客户端并在 UDP 中遇到问题。首先我使用主线程创建一个 TCP 线程来处理新的 accept() 并创建一个 UDP 线程来处理新的 recvfrom()。（TCP 案例没问题）一旦第一个 recvfrom() 回调，我尝试将客户端传递给新的 UDP 线程并保留当前线程以处理下一个新的 UDP 客户端它应该通过将地址和新创建的数据报套接字传递给新线程继续执行 recvfrom() 来工作，对吗？

在实验过程中，我发现旧的UDP线程一直在接收来自客户端的数据报，而新线程只是在做while循环和recvfrom()转为非阻塞方式，结果returns -1 .

所以我的代码有什么问题....谢谢~ 我是不是理解错了..?

PassToUDPThread 是我为将数据传递到新线程而创建的结构类型：

typedef struct {
   sockaddr_in ReceiverSocket;
   SOCKET sendSocket;
   char* recvbuf;
   long packet_size;

}PassToUDPThread;

这是我的第一个 UDP 线程函数的代码（仅处理第一个 recvfrom()）：

sockaddr_in *ReceiverSocket = new sockaddr_in;

ReceiverSocket->sin_family = AF_INET;
if (strcmp(recv_hostname, "INADDR_ANY") != 0)
inet_pton(AF_INET, ip_addr_char, &ReceiverSocket->sin_addr.s_addr);
else ReceiverSocket->sin_addr.s_addr = INADDR_ANY;
ReceiverSocket->sin_port = htons((u_short)recv_port);

//*** Create the socket
SOCKET s;

s = socket(AF_INET, SOCK_DGRAM, 0);
printf("Receiver: Socket Created - UDP connection\n");
bind(s, (struct sockaddr *)ReceiverSocket, sizeof(struct sockaddr_in));

do
{
   int fromlen = (int)sizeof(struct sockaddr_in);
   retVal = recvfrom(s, recvbuf, packet_size, 0, (struct sockaddr*)ReceiverSocket, &fromlen);
   std::cout << "UDP recv by MAIN "<<std::endl;
   if (retVal == SOCKET_ERROR) {
      std::cout << "UDP Socket error : " + WSAGetLastError()<<std::endl;
      return 0;
   }
   else {
       SOCKET sendSocket = socket(AF_INET, SOCK_DGRAM, 0);
       PassToUDPThread _p;
       PassToUDPThread *p = &_p;
       p->sendSocket = sendSocket;
       p->ReceiverSocket = *ReceiverSocket;
       p->recvbuf = recvbuf;
       p->packet_size = packet_size;

       thrd_t UDPthread;
       if (thrd_create(&UDPthread, ThreadUDPReceiver, (void*)p) == thrd_success) {
           std::cout<<"success create new UDP thread"<<std::endl;
                            }




   }
   } while (retVal>0);
     closesocket(s);
     UDPReceiver(arg);
     return 1;
}

这是新创建的 UDP 线程上的函数代码：

 int ThreadUDPReceiver(void *arg) {

    int retVal;
    SOCKET s = ((PassToUDPThread*)arg)->sendSocket;
    char* recvbuf = ((PassToUDPThread*)arg)->recvbuf;
    long packet_size = ((PassToUDPThread*)arg)->packet_size;
    sockaddr_in *ReceiverSocket = new sockaddr_in;
    memcpy(ReceiverSocket, &(((PassToUDPThread*)arg)->ReceiverSocket), sizeof sockaddr_in);

    bind(s, (struct sockaddr *)ReceiverSocket, sizeof(struct sockaddr_in));

    do {
       int fromlen = (int)sizeof(struct sockaddr_in);
       retVal = recvfrom(s, recvbuf, packet_size, 0, (struct sockaddr *)ReceiverSocket, &fromlen);
       std::cout << "UDP recv by thread "<< std::endl;
    } while (true);

    return 0;

    }

Answer 1

使用线程池。
摆脱额外的 UDP 套接字。使用同一个发送请求到达的响应。这样对客户来说也更简单。

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