C Socket初探 - 加入多線程支持，限制最大接入客戶端個數

先上一些多線程需要使用的函數定義：

DWORD WINAPI ProcessClientRequests(LPVOID lpParam)  //新線程將會執行的函數定義
{
      return 0;
}

HANDLE handler=CreateThread(NULL, 0, ProcessClientRequests, &clientsocket, 0, NULL);   //這里比較簡單，&clientsocket是個指針，是從主線程傳入新線程的參數


WaitForMultipleObjects(MAXCLIENTS, threads, TRUE, INFINITE);  //用來阻塞主線程，直到所有創建的子線程都完成任務為止，才繼續執行后面的代碼

for(int i=0;i<MAXCLIENTS; i++)
{
    CloseHandle(threads[i]);       //創建的每個子線程的HANDLE都會被保存在HANDLE數組中，這個函數用於關閉各個handle所對應的線程空間
}

 

先附上C Socket初探這篇文章的url

改造開始，客戶端程序沒有任何改動，因此此處略（請看C Socket初探中代碼所示）

 

服務器端程序

主線程代碼如下：

#define MAXCLIENTS 3           //宏定義，最多3個客戶端連接

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].\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)       //判斷是否已經超出最大連接數了
        {
            threads[existingClientCount++]=CreateThread(NULL, 0, ProcessClientRequests, &clientsocket, 0, NULL);  //啟動新線程，並且將socket傳入
        }
        else
        {
            char* msg="Exceeded Max incoming requests, will refused this connect!\r\n";
            send(clientsocket, msg, strlen(msg)+sizeof(char), NULL);       //發送拒絕連接消息給客戶端
            printf("***SYS***    REFUSED.\n");
            closesocket(clientsocket);                                     //釋放資源
 break;
        }
    }

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

    WaitForMultipleObjects(MAXCLIENTS, threads, TRUE, INFINITE);           //等待所有子線程，直到完成為止

    closesocket(s);
    for(int i=0;i<MAXCLIENTS; i++)
    {
        CloseHandle(threads[i]);                                           //清理線程資源
    }
    
    WSACleanup();

    printf("Cleared all.\r\n");

    getchar();

    exit(0);
}

子線程函數定義

DWORD WINAPI ProcessClientRequests(LPVOID lpParam)
{
    SOCKET* clientsocket=(SOCKET*)lpParam;  //這里需要強制轉換，注意：指針類型的

    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;
}

 

 

 

運行效果圖：