Winsock: Bind failing for client but not server

Seraphis · #1 30-Jun-2009, 12:04

Hello,

The title pretty much explains what's happening here... When I run the program I just return my own error code of 102; which means the bind on the client portion of the engine has failed.

Files

networkEngine.h

CPP / C++ / C Code:

#ifndef NETWORKENGINE_H
#define NETWORKENGINE_H

#include <winsock2.h>
#include <windows.h>

class networkEngine
{
public:
	int initWinsock(void);
	int bindSocket(void);
	
protected:
	WSADATA wsaData;
	SOCKADDR_IN sockAddr;
	SOCKET aSocket;
};

class networkClient : public networkEngine
{
public:
	~networkClient();
	int Connect(char addr[], int port);
};

class networkServer : public networkEngine
{
public:
	~networkServer();
	int Start(int port);
};

#endif

networkEngine.cpp

CPP / C++ / C Code:

#include "networkEngine.h"

#include <iostream>
using namespace std;

int networkEngine::initWinsock(void)
{
	if (WSAStartup(MAKEWORD(2,0), &wsaData) != 0)
		return 0;

	if (LOBYTE(wsaData.wVersion) != 2 || HIBYTE(wsaData.wVersion) != 0)
	{
		WSACleanup();
		return 0;
	}

	return 1;
}

int networkEngine::bindSocket(void)
{

	if (bind(aSocket, (SOCKADDR*)(&sockAddr), sizeof (sockAddr)) == SOCKET_ERROR)
		return 0;

	return 1;
}

networkClient::~networkClient()
{
	WSACleanup();

	if (aSocket != INVALID_SOCKET)
		closesocket(aSocket);
}

int networkClient::Connect(char addr[], int port)
{
	if (!initWinsock())
		return 101;

	sockAddr.sin_addr.S_un.S_addr = inet_addr(addr);
	sockAddr.sin_port = htons((u_short)port);
	sockAddr.sin_family = AF_INET;

	aSocket = socket(AF_INET, SOCK_STREAM, 0);
	
	if (!bindSocket())
		return 102;

	if (connect(aSocket, (SOCKADDR*)&sockAddr, sizeof(sockAddr)) == SOCKET_ERROR)
		return 103;
	
	return 1;
}

networkServer::~networkServer()
{
	WSACleanup();

	if (aSocket != INVALID_SOCKET)
		closesocket(aSocket);
}

int networkServer::Start(int port)
{
	if (!initWinsock())
		return 201;

	sockAddr.sin_addr.S_un.S_addr = INADDR_ANY;
	sockAddr.sin_family = AF_INET;
	sockAddr.sin_port = htons((u_short)port);

	aSocket = socket(AF_INET, SOCK_STREAM, 0);

	if (!bindSocket())
		return 202;

	listen(aSocket,SOMAXCONN);

	SOCKET newSocket = accept(aSocket, NULL, NULL);

	return 1;
}

main.cpp

CPP / C++ / C Code:

#include <iostream>
#include <conio.h>
#include "networkEngine.h"
using namespace std;

int main()
{
	int uin;

	cout << "1 - Server, 2 - Client" << endl;
	cin >> uin;

	if (uin == 1)
	{
		networkServer nServer;
		int errorCode = nServer.Start(2344);

		if (errorCode != 1)
			cout << "Error #" << errorCode << endl;
	}
	else
	{
		networkClient nClient;
		int errorCode = nClient.Connect("127.0.0.1", 2344);

		if (errorCode != 1)
			cout << "Error #" << errorCode << endl;
	}

	_getch();
	return 0;
}

I've been trying to figure this out... the server binds appropriately, which is odd.

Thanks in advance,
Seraphis.

davekw7x · #2 30-Jun-2009, 13:31

Quote:

Originally Posted by Seraphis

...the server binds appropriately...

Yes, you need to bind the server to a particular port so that clients can know how to connect.

However...

A client doesn't have to be bound to any particular port by the user. In your case, since the server and client are on the same machine, the client can not be bound to the same port that you have already committed to the server.

The kernel will choose a local port for the client when the connect() function is called for with server IP address and port number. In general, we don't care what the client's local port number is. See Footnote.

Bottom line: Don't call bind() for the client.

Regards,

Dave

Footnote: If you really want to know the client's local port number you can use getsockname():

CPP / C++ / C Code:

int networkClient::Connect(char addr[], int port)
{
    if (!initWinsock())
        return 101;

    sockAddr.sin_addr.S_un.S_addr = inet_addr(addr);
    sockAddr.sin_port = htons((u_short) port);
    sockAddr.sin_family = AF_INET;

    aSocket = socket(AF_INET, SOCK_STREAM, 0);

    // 
    // Do not bind the connection to any particluar port
    // davekw7c
    //if (!bindSocket())
        //return 102;

    if (connect(aSocket, (SOCKADDR *) & sockAddr, sizeof(sockAddr)) ==
        SOCKET_ERROR)
        return 103;

    int len = sizeof(sockAddr);
    if (getsockname(aSocket, (SOCKADDR *) &sockAddr, &len) < 0) {
        perror("getsockname");
        return 0;
    }
    else {
        cout << "Local port number after connect = "
             << htons(sockAddr.sin_port) << endl;
    }
    return 1;
}

But it's not really necessary to know this is it?

Seraphis · #3 30-Jun-2009, 14:17

Haven't touched winsock in a while... that makes sense. haha... I feel dumb now.

Thanks man for the quick response!

davekw7x · #4 30-Jun-2009, 18:46

Quote:

Originally Posted by Seraphis

... that makes sense...

Sometimes it makes sense, but after all these years, I still think there's a little magic in the "secret sauce" that lets this stuff work.

"Any sufficiently advanced technology is indistinguishable from magic."
---Arthur C Clarke: The third law of prediction

"Any sufficiently advanced magic is indistinguishable from technology."
---davekw7x: Comments on network programming

Regards,

Dave

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Winsock: Bind failing for client but not server

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