c++ - Winsock2 监听循环

Question

再次向精彩的 stackoverflow 社区问好!上次我问了一个问题，很快就解决了，我希望这会以同样的方式进行。 :)

所以我在玩 winsock，我希望能够同时将多个客户端连接到我的服务器。我觉得这可以通过线程创建、套接字创建、绑定(bind)和每次客户端连接时监听的循环来实现，但我这样做的努力只是出现了“监听失败并出现错误”。两种不同的取决于我尝试了什么。我用谷歌搜索只是为了找到高级 MSDN 示例，这些示例是最简单但仍然太难的示例。有人有任何简单的建议吗？(附带问题:我似乎无法让“mrecv()”返回整个“recvbuf”变量。我得到的只是一个字母。我知道这是我犯的新手错误, 但我就是想不通。:/这个问题可以等到以后再说。)

(这是到目前为止的服务器代码:)

#undef UNICODE

#define WIN32_LEAN_AND_MEAN

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <stdlib.h>
#include <stdio.h>
#include <iostream>

// Need to link with Ws2_32.lib
#pragma comment (lib, "Ws2_32.lib")
// #pragma comment (lib, "Mswsock.lib")

int minitialize();
int msend(char msendbuf[512]);
char mrecv();
int mshutdown();

#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT "10150"
 WSADATA wsaData;
 int iResult;

 SOCKET ListenSocket = INVALID_SOCKET;
 SOCKET ClientSocket = INVALID_SOCKET;

 struct addrinfo *result = NULL;
 struct addrinfo hints;

 int iSendResult;
 char recvbuf[DEFAULT_BUFLEN];
 int recvbuflen = DEFAULT_BUFLEN;

int main(void) 
{
    minitialize();
    mrecv();

    char mmessage[512];
    if (strncmp(mmessage,"shutdown",(strlen(mmessage))) == 0) {mshutdown();}
    std::cin.getline(mmessage, 512);
    msend(mmessage);

    // shutdown the connection since we're done
    mshutdown();
    std::cin.ignore();

    return 0;
}

int msend(char msendbuf[512])   // Send a message
{
    int iResult3 = send( ClientSocket, msendbuf, 512, 0 );
    if (iResult3 == SOCKET_ERROR) {
        printf("send failed with error: %d\n", WSAGetLastError());
        closesocket(ClientSocket);
        WSACleanup();
        return 1;
    }

    printf("Bytes Sent: %ld\n", iResult);
            std::cout<<"msendbuf: "<<msendbuf<<"\n";
            std::cin.ignore();
}

char mrecv() //Recieve a message
{
    int iResult2 = recv(ClientSocket, recvbuf, 512, 0);
        if (iResult2 > 0) {
            printf("Bytes received: %d\n", iResult2);
        std::cout<<"recvbuf: "<<recvbuf<<"\n";
        }
        else if (iResult2 == 0)
            printf("Connection closing...\n");
        else  {
            printf("recv failed with error: %d\n", WSAGetLastError());
            closesocket(ClientSocket);
            WSACleanup();
            return 1;
        }
    return *recvbuf;
}

int minitialize()   //initialize the winsock server
{
    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != 0) {
        printf("WSAStartup failed with error: %d\n", iResult);
        return 1;
    }

    ZeroMemory(&hints, sizeof(hints));
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_flags = AI_PASSIVE;

    // Resolve the server address and port
    iResult = getaddrinfo(NULL, DEFAULT_PORT, &hints, &result);
    if ( iResult != 0 ) {
        printf("getaddrinfo failed with error: %d\n", iResult);
        WSACleanup();
        return 1;
    }

    // Create a SOCKET for connecting to server
    ListenSocket = socket(result->ai_family, result->ai_socktype, result->ai_protocol);
    if (ListenSocket == INVALID_SOCKET) {
        printf("socket failed with error: %ld\n", WSAGetLastError());
        freeaddrinfo(result);
        WSACleanup();
        return 1;
    }

    // Setup the TCP listening socket
    iResult = bind( ListenSocket, result->ai_addr, (int)result->ai_addrlen);
    if (iResult == SOCKET_ERROR) {
        printf("bind failed with error: %d\n", WSAGetLastError());
        freeaddrinfo(result);
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }

    freeaddrinfo(result);

    iResult = listen(ListenSocket, SOMAXCONN);
    if (iResult == SOCKET_ERROR) {
        printf("listen failed with error: %d\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }

    // Accept a client socket
    ClientSocket = accept(ListenSocket, NULL, NULL);
    if (ClientSocket == INVALID_SOCKET) {
        printf("accept failed with error: %d\n", WSAGetLastError());
        closesocket(ListenSocket);
        WSACleanup();
        return 1;
    }

    // No longer need server socket
    closesocket(ListenSocket);
}

int mshutdown()     //shutdown the server
{
    iResult = shutdown(ClientSocket, SD_SEND);
    if (iResult == SOCKET_ERROR) {
        printf("shutdown failed with error: %d\n", WSAGetLastError());
        closesocket(ClientSocket);
        WSACleanup();
        return 1;
    }

    // cleanup
    closesocket(ClientSocket);
    WSACleanup();
    return 0;
}

是的，如果您想知道的话，我正计划将所有这些全局变量放入它们各自的局部函数中。我现在只需要他们在那里清理一些困惑，它似乎没有引起任何问题。

Answer 1

mrecv() 定义为

char mrecv()。

在函数mrecv() 中，它返回一个字符串。因为 mrecv() 根据定义应该返回一个字符，所以返回 recvbuf 的第一个字符。编译器不会提示 return *recvbuf。即使意图返回单个字符，这在语法上也是正确的。

accept() 返回一个文件描述符给客户端的连接。 accept() 返回后，您可以生成一个新进程来使用此描述符处理消息，同时原始进程返回接受连接。或者您可以创建一个新线程来处理来自此描述符的消息，同时原始线程恢复接受连接。您将需要循环 accept()。

这是一个可用于服务器的骨架模板。您已经在 minitialize() 上正确设置了所有内容。在下面的示例代码中，mrecv() 接受一个参数，即连接的客户端的文件描述符，newconn。

socket()
bind()
listen(mysock, 10);
while(keep listening) {
    newconn = accept(mysock, &peeraddr, &peeraddrlen)
    if(newconn > 0) {
        if(CreateThread(<security attribute>, <stack size>, (void *)&mrecv, (void *)&newconn, <creation flag>, <threadid>))
            perror("Unable to create thread\n");
    }
}
closesocket(mysock)