C++ WinSock 2 - 使用 getpeername() 函数时套接字崩溃

Question

每当我使用函数getpeername() 时，我的程序在调试时崩溃并返回255。它printf 是主机名，当它开始尝试printf 对等名称时，它会显示“对等名称：”，然后在它告诉我对等名称之前崩溃。我知道这个程序没有多大意义。我只是在弄乱一些 WinSock 2 函数，看看它们都做了什么。

我的代码：

#include <windows.h>
#include <winsock2.h>
#include <conio.h>
#include <stdio.h>
#include <iostream>
using namespace std;
#define SCK_VERSION2 0x0202
#define DEFAULT_BUFLEN 512
#define DEFAULT_PORT 27015

int main() {
    //----------------------
    // Declare and initialize variables.
    WSADATA wsaData;
    int iResult;

    SOCKET ConnectSocket = INVALID_SOCKET;
    struct sockaddr_in clientService;

    char name[500] = "";

    sockaddr sName;
    int sNameSize =  sizeof(sName);

    char *sendbuf = "Test";
    char recvbuf[DEFAULT_BUFLEN];
    int recvbuflen = DEFAULT_BUFLEN;

    //----------------------
    // Initialize Winsock
    iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
    if (iResult != NO_ERROR) {
      printf("WSAStartup failed: %d\n", iResult);
      return 1;
    }

    //----------------------
    // Create a SOCKET for connecting to server
    ConnectSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (ConnectSocket == INVALID_SOCKET) {
        printf("Error at socket(): %i\n", WSAGetLastError() );
        WSACleanup();
        return 1;
    }

    //----------------------
    // The sockaddr_in structure specifies the address family,
    // IP address, and port of the server to be connected to.
    clientService.sin_family = AF_INET;
    clientService.sin_addr.s_addr = inet_addr( "127.0.0.1" );
    clientService.sin_port = htons(444);

    //----------------------
    // Connect to server.
    iResult = connect( ConnectSocket, (SOCKADDR*) &clientService, sizeof(clientService) );
    if ( iResult == SOCKET_ERROR) {
        closesocket (ConnectSocket);
        printf("Unable to connect to server: %i\n", WSAGetLastError());
        WSACleanup();
        return 1;
    }

    //----------------------
    //Get local host name
    iResult = gethostname(name, sizeof(name));
    if (iResult == NO_ERROR) {
        printf("Host Name: %s\n", name);
    }
    else if (iResult == SOCKET_ERROR) {
        printf("Could not resolve host name: %i", WSAGetLastError());
    }

    iResult = getpeername(ConnectSocket, (struct sockaddr*)&sName, &sNameSize);
    if (iResult == NO_ERROR)
        printf("Peer Name: %s", sName);
    else if (iResult == SOCKET_ERROR)
        printf("Could not get peer name: %i", WSAGetLastError());

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

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

    // shutdown the connection since no more data will be sent
    iResult = shutdown(ConnectSocket, SD_SEND);
    if (iResult == SOCKET_ERROR) {
        printf("shutdown failed: %d\n", WSAGetLastError());
        closesocket(ConnectSocket);
        WSACleanup();
        return 1;
    }

    // Receive until the peer closes the connection
    do {

        iResult = recv(ConnectSocket, recvbuf, recvbuflen, 0);
        if ( iResult > 0 )
            printf("Bytes received: %s\n", recvbuf); //printf("Bytes received: %d\n", iResult);
        else if ( iResult == 0 )
            printf("Connection closed\n");
        else
            printf("recv failed: %d\n", WSAGetLastError());

    } while( iResult > 0 );

    // cleanup
    closesocket(ConnectSocket);
    WSACleanup();
    system("PAUSE");
    return 0;
}

Answer 1

试试这个：

结构 sockaddr_in sockaddr; int namelen = sizeof(sockaddr); if(!getpeername(socket, (struct sockaddr *)&sockaddr, &namelen)) { printf("对端名称：%s\n", inet_ntoa((in_addr)(* (in_addr*)&sockaddr.sin_addr.S_un.S_addr))); }

Answer 2

你的电话有两个问题。

1. 您的套接字是 IPv4 套接字，因此 getpeername() 需要 sockaddr_in，就像 connect() 一样。但是您已将 sName 变量声明为 sockaddr。您需要为套接字类型使用正确的结构类型：

   sockaddr_in sName;
   

2. 您正试图打印出sName，就好像它是一个以空字符结尾的字符串一样，但事实并非如此。它是一个二进制结构。您必须将其内容转换为以 null 结尾的字符串，例如 inet_ntoa()：

   iResult = getpeername(ConnectSocket, (struct sockaddr*)&sName, &sNameSize);
   if (iResult == 0)
       printf("Peer Name: %s", inet_ntoa(sName.sin_addr));
   else
       printf("Could not get peer name: %i", WSAGetLastError());