c++ - 在 Visual C++ 中接受来自客户端(套接字编程)的连接的问题

Question

我在 Visual C++ 中编写了一个简单的单线程客户端服务器应用程序.当我运行我的服务器时，我等待一段时间它接受来自客户端的一些请求。

当我将客户端连接到服务器时。客户端上的日志消息报告 14 个字节已发送，服务器上没有消息。我已经编写了一个打印语句来打印控制台上服务器接受的任何内容，但服务器不打印任何内容。

在我看来，客户端已连接到其他服务器。

客户端和服务器代码如下。

服务器代码

#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <iphlpapi.h>
#include <stdio.h>
#include <conio.h>

#define DEFAULT_PORT        "27015"
#define DEFAULT_BUFLEN        512
#pragma comment(lib, "Ws2_32.lib")

int main() {
    WSADATA wsdata;
    int result = WSAStartup(MAKEWORD(2,2),&wsdata);
    if (result != 0){
        printf("%s","Unable to initilize windows socket\n");
        getch();
        return 1;
    }

    struct addrinfo *addrResult = NULL,hints;
    ZeroMemory(&hints, sizeof (hints));

    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_flags = AI_PASSIVE;

    result = getaddrinfo(NULL,DEFAULT_PORT,&hints,&addrResult);
    if (result != 0){
        printf("%s","Error in getaddrInfo");
        getch();
        return 1;
    }
    SOCKET listenSocket = INVALID_SOCKET;
    listenSocket = socket(addrResult->ai_family,addrResult->ai_socktype,addrResult->ai_protocol);

    if (listenSocket == INVALID_SOCKET){
        printf("%s","Error in creating socket object\n");
        getch();
        closesocket(listenSocket);
        WSACleanup();
        return 1;
    }

    sockaddr_in service;
    service.sin_family = AF_INET;
    service.sin_addr.s_addr = inet_addr("127.0.0.1");
    service.sin_port = htons(27015);

    if (bind(listenSocket,addrResult->ai_addr,
        (int)addrResult->ai_addrlen) == SOCKET_ERROR){
    //if(bind(listenSocket,(SOCKADDR*) &service,
    //    sizeof(service)) == SOCKET_ERROR){

        printf("bind failed: %d\n", WSAGetLastError());
        freeaddrinfo(addrResult);
        closesocket(listenSocket);
        WSACleanup();
        getch();
        return 1;
    }
    freeaddrinfo(addrResult);
    if (listen(listenSocket,SOMAXCONN) == SOCKET_ERROR){
        printf("%s","Error in listening socket");
        getch();
        closesocket(listenSocket);
        WSACleanup();
    }
    SOCKET clientSocket = INVALID_SOCKET;
    clientSocket = accept((listenSocket,NULL,NULL);
    if (clientSocket ==  INVALID_SOCKET){
        closesocket(listenSocket);
        WSACleanup();
    }

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

    do{
        iRecvResult = 0;
        iSendResult = 0;
        iRecvResult = recv(clientSocket,recvbuf,recvbuflen,0);
        if (iRecvResult > 0){
            printf("Bytes received: %d\n", iRecvResult);
            getch();
            // Echo the buffer back to the sender
            iSendResult = send(clientSocket, recvbuf, iRecvResult, 0);
            if (iSendResult == SOCKET_ERROR) {
                printf("send failed: %d\n", WSAGetLastError());
                closesocket(clientSocket);
                WSACleanup();
                return 1;
            }
            printf("Bytes sent: %d\n", iSendResult);
        }
        else if (iRecvResult == 0){
            printf("Connection closing...\n");
        }
        else{
            printf("recv failed: %d\n", WSAGetLastError());
            closesocket(clientSocket);
            WSACleanup();
            return 1;
        }
    }while(iRecvResult > 0);
  getch();
  return 0;
}

客户端代码

#ifndef WIN32_LEAN_AND_MEAN
#define WIN32_LEAN_AND_MEAN
#endif

#include <windows.h>
#include <winsock2.h>
#include <ws2tcpip.h>
#include <iphlpapi.h>
#include <stdio.h>
#include <conio.h>

#define DEFAULT_PORT        "27015"
#define DEFAULT_BUFLEN        512
#pragma comment(lib, "Ws2_32.lib")

int main(){
    WSADATA wsdata;
    WSAStartup(MAKEWORD(2,2),&wsdata);
    struct addrinfo *addrResult = NULL,hints;
    ZeroMemory(&hints, sizeof (hints));
    hints.ai_protocol = IPPROTO_TCP;
    hints.ai_socktype = SOCK_STREAM;
    hints.ai_family = AF_UNSPEC;
    int result = 0;
    if (getaddrinfo("127.0.0.1",DEFAULT_PORT,
        &hints,&addrResult)){
            printf("%s","Error in getaddrInfo\n");
            WSACleanup();
            getch();
            return 1;
    }
    SOCKET connectingSocket = INVALID_SOCKET;
    connectingSocket = socket(addrResult->ai_family,addrResult->ai_socktype,
        addrResult->ai_protocol);
    if (connectingSocket == INVALID_SOCKET){
        printf("%s","Error in creating socket\n");
        freeaddrinfo(addrResult);
        WSACleanup();
        getch();
        return 1;
    }

    if (connect(connectingSocket,addrResult->ai_addr, (int)addrResult->ai_addrlen) != 0){
        closesocket(connectingSocket);
        connectingSocket = INVALID_SOCKET;
        WSACleanup();

    }
    freeaddrinfo(addrResult);

    int recvbuflen = DEFAULT_BUFLEN;
    char *sendbuf = "this is a test";
    char recvbuf[DEFAULT_BUFLEN];

    int iResult;

    // Send an initial buffer
    iResult = send(connectingSocket, sendbuf, (int) strlen(sendbuf), 0);
    if (iResult == SOCKET_ERROR) {
        printf("send failed: %d\n", WSAGetLastError());
        closesocket(connectingSocket);
        WSACleanup();
        return 1;
    }

    printf("Bytes Sent: %ld\n", iResult);

    // shutdown the connection for sending since no more data will be sent
    // the client can still use the connectingSocket for receiving data
    iResult = shutdown(connectingSocket, SD_SEND);
    if (iResult == SOCKET_ERROR) {
        printf("shutdown failed: %d\n", WSAGetLastError());
        closesocket(connectingSocket);
        WSACleanup();
        return 1;
    }

    // Receive data until the server closes the connection
    do {
        iResult = recv(connectingSocket, recvbuf, recvbuflen, 0);
        if (iResult > 0)
            printf("Bytes received: %d\n", iResult);
        else if (iResult == 0)
            printf("Connection closed\n");
        else
            printf("recv failed: %d\n", WSAGetLastError());
    } while (iResult > 0);

    getch();
    return 0;
}

Answer 1

嗯...在修复明显的语法错误(clientSocket = accept((listenSocket,NULL,NULL);)中不匹配的左括号后，它似乎工作得相当好我。在服务器上我得到:

Bytes received: 14
Bytes sent: 14
Connection closing...

在客户端:

Bytes Sent: 14
Bytes received: 14
recv failed: 10054

因此，客户端向服务器发送 14 个字节(您按下回车)，服务器将这 14 个字节回显给客户端(您再次按下回车)，然后服务器关闭连接。客户端读取这 14 个字节，然后在连接关闭时进一步读取失败。

编辑:我通过打开两个 Windows SDK 命令提示窗口运行代码，在一个窗口中运行 server，在另一个窗口中运行 client —— 没有什么特别令人兴奋或不寻常的一个。