在 TCP_Client 程序中输入用户名后出现 "Debug assertion failed" 错误

Question

我目前是自动化和应用信息学专业的学生。我有一个来自计算机网络的项目，我需要在线程的帮助下制作一个聊天应用程序。从现在开始，我为服务器创建了连接的接收部分并创建了客户端，但是当我运行程序时，我得到了一个调试断言失败的错误。到目前为止，我只有用户连接部分。我真的需要一些帮助，因为我被困住了。

tcp_server.cpp

#include "winsock2.h"
#include "ClientThread.h"
#include <stdio.h>
#include <string.h>
#include <vector>
#include "ws2tcpip.h"
#pragma comment(lib,"ws2_32.lib")

const unsigned int SysThread::INFINIT_WAIT = UINT_MAX;

void main()
{
    WSADATA wsaData;
    int iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != NO_ERROR) {
        printf("Error at WSAStartup()\n");
        return;
    }

    // Socket for listening for incoming requests
    SOCKET ListenSocket;
    ListenSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (ListenSocket == INVALID_SOCKET) {
        printf("Error at the listening socket, error code: %d\n", WSAGetLastError);
        WSACleanup();
        return;
    }

    int Port = 1300;
    char IP[10] = "127.0.0.1";
    sockaddr_in ServerAddress;
    int ServerLen = sizeof(ServerAddress);

    ServerAddress.sin_family = AF_INET;
    ServerAddress.sin_port = htons(Port);
    inet_pton(AF_INET, IP, &ServerAddress.sin_addr);

    if (bind(ListenSocket, (SOCKADDR*)&ServerAddress, sizeof(ServerAddress)) == SOCKET_ERROR) {
        printf("bind() failed.\n");
        closesocket(ListenSocket);
        WSACleanup();
        return;
    }

    if (listen(ListenSocket, 1) == SOCKET_ERROR) {
        printf("Error listening on socket.\n");
        WSACleanup();
        return;
    }

    std::vector <char*> username;
    int RecUserLen = 100;
    char RecUser[100];
    int ReceiveTheUsername;

    // Socket for accepting incoming requests
    SOCKET AcceptSocket;
    printf("Waiting for client to connect...\n");

    while (AcceptSocket = accept(ListenSocket, NULL, NULL)) {
        printf("Succesful connection.\n");
        int UserNum = 1;
        ReceiveTheUsername = recv(AcceptSocket, RecUser, RecUserLen-1, 0);
        username[UserNum] = RecUser;
        printf("Username: %s", username[UserNum]);
    }
}

tcp_client.cpp

#include <iostream>
#include <stdio.h>
#include <string.h>
#include "winsock2.h"
#include "ws2tcpip.h"
#pragma comment(lib, "ws2_32.lib")
void main()
{
    int iResult;
    //----------------------
    WSADATA wsaData;
    iResult = WSAStartup(MAKEWORD(2, 2), &wsaData);
    if (iResult != NO_ERROR)
        printf("Hiba a WSAStartup() –nál\n");
    //----------------------

    SOCKET ClientSocket;
    ClientSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);

    if (ClientSocket == INVALID_SOCKET)
    {
        printf("Error at initializing the socket, error code: %ld\n",
            WSAGetLastError());
        WSACleanup();
        return;
    }
    //---------------------
    int Port = 1300;
    char IP[10] = "127.0.0.1";
    sockaddr_in ServerAddr;
    int AddrLen = sizeof(ServerAddr);

    ServerAddr.sin_family = AF_INET;
    inet_pton(AF_INET, "127.0.0.1", &ServerAddr.sin_addr);
    ServerAddr.sin_port = htons(Port);
    //----------------------
   
    if (connect(ClientSocket, (SOCKADDR*)&ServerAddr, AddrLen) == SOCKET_ERROR)
    {
        printf("Connect error, error code: %ld\n",
            WSAGetLastError());
        WSACleanup();
        return;
    }
    else {
        printf("Succesful connection.\n");
    }
    //----------------------

    char UserName[100];
    printf("Enter the username: ");
    fgets(UserName, 100, stdin);

    int SendUsername;
    SendUsername = send(ClientSocket, Felhasznalonev, sizeof(Felhasznalonev),0);
    if (SendUsername == SOCKET_ERROR) {
        printf("Error at sending the username.\n");
        closesocket(ClientSocket);
        WSACleanup();
        return;
    }

    closesocket(ClientSocket);
    WSACleanup();
    return;
}

Answer 1

这里有一个明显的问题

std::vector <char*> username;
...
int UserNum = 1;
...
username[UserNum] = RecUser;

username 是零大小向量，因此 username[UserNum] 是越界向量访问。

不太确定您为什么要使用向量，它没有像当前那样向代码中添加任何内容。但是，如果您确实需要使用一个，请确保它足够大。

Answer 2

debug assertion failed错误的原因如John所说，你没有设置vector <char*> username的大小，所以你不能通过赋值直接设置vector中的值

但是你输出乱码的原因是你读取的字节数超过了实际returned的字节数

根据 document:

Return value If no error occurs, recv returns the number of bytes received and the buffer pointed to by the buf parameter will contain this data received. If the connection has been gracefully closed, the return value is zero.

Otherwise, a value of SOCKET_ERROR is returned, and a specific error code can be retrieved by calling

所以recv函数的return值（在代码中是ReceiveTheUsername）实际上是实际读取的字节数，而不是RecUserLen-1，所以你可以使用 ReceiveTheUsername 来确定 returned 字符串长度的有效性。

只需要像下面的代码一样把字符串初始化为空，就可以防止乱码。（当然你也可以根据字符数手动加上'\0'return ed，或者根据字符长度截取对应的字符串。)

char RecUser[100] = "";
while (AcceptSocket = accept(ListenSocket, NULL, NULL)) {
    printf("Succesful connection.\n");
    ReceiveTheUsername = recv(AcceptSocket, RecUser, RecUserLen - 1, 0);
    username.push_back(RecUser);
    printf("Username: %s", username.back());
}

在 TCP_Client 程序中输入用户名后出现 "Debug assertion failed" 错误

I get a "Debug assertion failed" error after entering the username in my TCP_Client program

c++

winapi

multithreading

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