std::exception while starting server (WinSock2)

Question

I am new to C++ and I am currently learning from a tutorial how to use winsock(2).
However I run into a problem with my server. I have no idea how it happens.

#include "stdafx.h"
#include <WinSock2.h>
#include <winsock.h>

#pragma comment(lib, "Ws2_32.lib")

using namespace std;

void cmdError(string e = ""){
    cout << "Error:\n" << e << endl;
    chrono::milliseconds t( 3000 );
    this_thread::sleep_for( t );
}

void startServer(int port){
    SOCKET acceptSocket;
    SOCKET connectedSocket;
    SOCKADDR_IN addr;
    addr.sin_family=AF_INET;
    addr.sin_port=htons(port);
    addr.sin_addr.s_addr=ADDR_ANY;
    memset(&addr, 0, sizeof(SOCKADDR_IN));
    long rc;
    acceptSocket = socket(AF_INET, SOCK_STREAM, 0);
    if(acceptSocket = INVALID_SOCKET){ throw new exception();}
    rc = ::bind(acceptSocket, (SOCKADDR*) &addr, sizeof(SOCKADDR_IN));
    if(rc == SOCKET_ERROR){ throw new exception();}
    rc = listen(acceptSocket, 10);
    if(rc == SOCKET_ERROR){ throw new exception();}
    connectedSocket = accept(acceptSocket, NULL, NULL);
    if(connectedSocket == INVALID_SOCKET){ throw new exception();}
}

void startClient(string ip, int port){
    long rc;
    SOCKADDR_IN addr;
    SOCKET s = socket(AF_INET, SOCK_STREAM, 0);
    if(s == INVALID_SOCKET){ throw new exception();}

    memset(&addr, 0, sizeof(SOCKADDR_IN));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(port);
    addr.sin_addr.s_addr = inet_addr(ip.c_str());
    rc = connect(s, (SOCKADDR*)&addr, sizeof(SOCKADDR));

    if(s == SOCKET_ERROR){ throw new exception();}
}

int _tmain(int argc, _TCHAR* argv[]){
    WSADATA wsa;
    if(WSAStartup(MAKEWORD(2, 0), &wsa) != 0){
        cmdError();
        return 1;
    }
    string n;
    int port;
    cout << "Please specify the task of this thread. \nEnter 'server' or 'client'." << endl;
    getline(cin, n);
    system("cls");
    cout << "Please specify a port." << endl;
    cin.clear();
    cin.sync();
    cin >> port;
    system("cls");
    if(n.at(0) == 'c' || n.at(0) == 'C'){
        string ip;
        cout << "You started a client application." << endl;
        cout << "Enter the IP address of the server you want to connect to." << endl;
        cin.clear();
        cin.sync();
        getline(cin, ip);
        system("cls");
        cmdError();
        try{
            startClient(ip, port);
        }
        catch(exception e){
            cmdError();
            e.~exception();
            return 1;
        }

        return 0;
    }
    else if(n.at(0) == 's' || n.at(0) == 'S'){
        cout << "You started a server application" << endl;
        try {
            startServer(port);
        }
        catch(exception e){
            e.~exception();
            return 1;
        }
        return 0;
    }
    cmdError();
    return 1;
}

void sendStr(string msg){
}

When I start my server through the application I get the following error popup in void startServer(int port).

First-chance exception at 0x7667C42D in test.exe: Microsoft C++ exception:
std::exception at memory location 0x001EF5C8.

If there is a handler for this exception, the progrram may be safely continued.

Any idea why this is happening?

Answer 1

You're not catching what you're throwing. You're throwing an exception * and you're trying to catch an exception.

You should almost never throw a new exception, you should just throw an exception, you should then catch a const reference to said exception, so for example:

#include <exception>
#include <iostream>

int
x(int y)
{
    throw std::exception();
}

int
main(int argc, char **argv)
{
    try {
        x(2);
    } catch (const std::exception &e) {
        std::cout << "Oops" << std::endl;
    }
    return 0;
}

If I used your code I get the program terminated due to an uncaught exception of type std::exception * (note that it's a pointer to std::exception, not a std::exception.

In addition, I have no idea what you're trying to accomplish with the e.~exception();. It has no place in that code. If you were trying to delete the exception that you had newd, then you should delete it. Explicit calls to destructors like this indicates that you're having difficulties understanding the object lifecycle; which is a fundamental part of the C++ language.

Charles Bailey's answer to this question goes into some detail on the whys and whats of this also.