c语言socket多线程编程限制客户端连接数

先上一些多线程需要使用的函数定义：

HANDLE handler=CreateThread(NULL, 0, ProcessClientRequests, &clientsocket, 0, NULL);   //这里比较简单，&clientsocket是个指针，是从主线程传入新线程的参数

WaitForMultipleObjects(MAXCLIENTS, threads, TRUE, INFINITE);  //用来阻塞主线程，直到所有创建的子线程都完成任务为止，才继续执行后面的代码

for(int i=0;i<MAXCLIENTS; i++)
{
    CloseHandle(threads[i]);       //创建的每个子线程的HANDLE都会被保存在HANDLE数组中，这个函数用于关闭各个handle所对应的线程空间
}
</div>

服务器端程序

主线程代码如下：

int main()
{
    WSADATA wsaData;
    WSAStartup(MAKEWORD(2, 2), &wsaData);
    HANDLE threads[MAXCLIENTS];

    SOCKET s=socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);

    sockaddr_in sockaddr;
    sockaddr.sin_family=PF_INET;
    sockaddr.sin_addr.S_un.S_addr=inet_addr("127.0.0.1");
    sockaddr.sin_port=htons(9000);
    bind(s, (SOCKADDR*)&sockaddr, sizeof(SOCKADDR));

    listen(s, 1);

    printf("listening on port [%d].\n", 9000);

    int existingClientCount=0;
    while(TRUE)
    {
        SOCKADDR clientAddr;
        int size=sizeof(SOCKADDR);

        SOCKET clientsocket;
        clientsocket=accept(s, &clientAddr, &size);
        printf("***SYS***    New client touched.\n");

        if(existingClientCount<MAXCLIENTS)       //判断是否已经超出最大连接数了
        {
            threads[existingClientCount++]=CreateThread(NULL, 0, ProcessClientRequests, &clientsocket, 0, NULL);  //启动新线程，并且将socket传入
        }
        else
        {
            char* msg="Exceeded Max incoming requests, will refused this connect!\r\n";
            send(clientsocket, msg, strlen(msg)+sizeof(char), NULL);       //发送拒绝连接消息给客户端
            printf("***SYS***    REFUSED.\n");
            closesocket(clientsocket);                                     //释放资源
            break;
        }
    }

    printf("Maximize clients occurred for d%.\r\n", MAXCLIENTS);

    WaitForMultipleObjects(MAXCLIENTS, threads, TRUE, INFINITE);           //等待所有子线程，直到完成为止

    closesocket(s);
    for(int i=0;i<MAXCLIENTS; i++)
    {
        CloseHandle(threads[i]);                                           //清理线程资源
    }

    WSACleanup();

    printf("Cleared all.\r\n");

    getchar();

    exit(0);
}
</div>

子线程函数定义

    char* msg="Hello, my client.\r\n";
    send(*clientsocket, msg, strlen(msg)+sizeof(char), NULL);
    printf("***SYS***    HELLO.\n");

    while(TRUE)
    {
        char buffer[MAXBYTE]={0};
        recv(*clientsocket, buffer, MAXBYTE, NULL);
        if(strcmp(buffer, "exit")==0)
        {
            char* msg_bye="Bye.\r\n";
            send(*clientsocket, msg_bye, strlen(msg_bye)+sizeof(char), NULL);
            break;
        }
        printf("***Client***    %s\n", buffer);
    }

    closesocket(*clientsocket);

    return 0;
}
</div>