C Socket初探

先上一些多线程需要使用的函数定义：

DWORD WINAPI ProcessClientRequests(LPVOID lpParam)  //新线程将会执行的函数定义
{
      return 0;
}

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
}

先附上C Socket初探这篇文章的url

改造开始，客户端程序没有任何改动，因此此处略（请看C Socket初探中代码所示）

服务器端程序

主线程代码如下：

#define MAXCLIENTS 3           //宏定义，最多3个客户端连接

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].
", 9000);

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

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

        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!
";
            send(clientsocket, msg, strlen(msg)+sizeof(char), NULL);       //发送拒绝连接消息给客户端
            printf("***SYS***    REFUSED.
");
            closesocket(clientsocket);                                     //释放资源
            break;
        }
    }

    printf("Maximize clients occurred for d%.
", 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.
");

    getchar();

    exit(0);
}

子线程函数定义

DWORD WINAPI ProcessClientRequests(LPVOID lpParam)
{
    SOCKET* clientsocket=(SOCKET*)lpParam;  //这里需要强制转换，注意：指针类型的

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

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

    return 0;
}

运行效果图：