Hello,

I am having a trouble with the proxy I am making with C++.

I am connecting a client to a server trough my program.

client talks to my program, program talks to server
server talks to my program, program talks to client

Like that. However, when I receive something from the client and send it to the server, it all goes fine. But when I receive from the server - which goes fine - and try to send to the client something goes terribly wrong.

Which happens in the cltosv function.

#include <cstdio>
#include <winsock2.h>
#include <iostream>
#include <string>

using namespace std;

struct incSockets
{
	SOCKET* sv;
	SOCKET* cl;
	sockaddr_in* clSockAddr;
	sockaddr_in* svSockAddr;
};

void filter( char* packet, int nPacketLen )
{
	while (nPacketLen > 0)
	{
		cout << "(" << int(*packet) << ")";
		//cout << "" << (*packet) << "";
		packet++;
		nPacketLen--;
	}
	cout << endl;
}

//
//	Error String
//

char *ErrText( int err )
{
	// Displays a nicer error message.
}

DWORD WINAPI svtocl(void* param)
{
	cout << "Arived in thread SVTOCL" << endl;
	struct incSockets* incs = static_cast<struct incSockets*>(param);
	
	SOCKET cl = *incs->cl;
	SOCKET sv = *incs->sv;
	sockaddr_in clSockAddr = *incs->clSockAddr;
	sockaddr_in svSockAddr = *incs->svSockAddr;
	
	char buffer[20480];
	size_t bytesReceived;
	int fromlen = sizeof(svSockAddr);
	int bytes_sent;

	while(true){
		bytesReceived = recvfrom(sv, buffer, 20480, 0, (struct sockaddr *)&svSockAddr, &fromlen);
				
		if(bytesReceived == 4294967295) {
			cout << "Servers: " << ErrText(WSAGetLastError()) << endl;
		}
		else if(bytesReceived > 0)
		{
			cout << "Server: ";
			filter(buffer, bytesReceived);
			bytes_sent = sendto(cl, buffer, bytesReceived, 0, (struct sockaddr*)&clSockAddr, sizeof(struct sockaddr_in));
			
			//cout << "Bytes Sent: " << bytes_sent << endl;
			
			if(bytes_sent < 0)
			{
				cout << ErrText(WSAGetLastError()) << endl;
			}
		}
		else
		{
			cout << "Server bytes: " << bytesReceived << endl;
		}
	}	
}

DWORD WINAPI cltosv(void* param)
{
	cout << "Arived in thread CLTOSV" << endl;
	struct incSockets* incs = static_cast<struct incSockets*>(param);
	
	SOCKET cl = *incs->cl;
	SOCKET sv = *incs->sv;
	sockaddr_in clSockAddr = *incs->clSockAddr;
	sockaddr_in svSockAddr = *incs->svSockAddr;

	char buffer[20480];
	size_t bytesReceived;
	int fromlen = sizeof(clSockAddr);
	int bytes_sent;

	while(true){
	
		//bytesReceived = recvfrom(cl, buffer, sizeof(buffer), 0, &client, &client_length);
		bytesReceived = recvfrom(cl, buffer, 20480, 0, (struct sockaddr *)&clSockAddr, &fromlen);
				
		if(bytesReceived == 4294967295) {
			//cout << "Client: " << ErrText(WSAGetLastError()) << endl;
		}
		else if(bytesReceived > 0)
		{
			cout << "Client: ";	
			filter(buffer, bytesReceived);
			bytes_sent = sendto(sv, buffer, bytesReceived, 0, (struct sockaddr*)&svSockAddr, sizeof(struct sockaddr_in));
			
			cout << "Bytes Sent: " << bytes_sent << endl;
			
			if(bytes_sent < 0)
			{
				cout << ErrText(WSAGetLastError()) << endl;
			}
		}	
	}			
	
}

int main(int argc, char** argv) {

	struct incSockets incs;

	const int iReqWinsockVer = 2;   

	WSADATA wsaData;

	if (WSAStartup(MAKEWORD(iReqWinsockVer,0), &wsaData)==0)
	{
		if (LOBYTE(wsaData.wVersion) >= iReqWinsockVer)
		{
			SOCKET cl = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
			SOCKET sv = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
						
			if (cl==INVALID_SOCKET)
			{
				cout << "1" << ErrText(WSAGetLastError()) << endl;
			}
			
			if(sv == INVALID_SOCKET)
			{
				cout << "2" << ErrText(WSAGetLastError()) << endl;
			}
					
			sockaddr_in clSockAddr;
			
			memset(&clSockAddr, 0, sizeof(clSockAddr));
			
			clSockAddr.sin_family = AF_INET;
			clSockAddr.sin_port = htons(1339);
			clSockAddr.sin_addr.S_un.S_addr = INADDR_ANY;

			if (bind(cl, (sockaddr*)(&clSockAddr), sizeof(clSockAddr))!=0)
			{
				cout << "3" << ErrText(WSAGetLastError()) << endl;		
			}
									
			sockaddr_in svSockAddr;
			
			memset(&svSockAddr, 0, sizeof(svSockAddr));

			svSockAddr.sin_family = AF_INET;
			svSockAddr.sin_port = htons(7777);
			svSockAddr.sin_addr.S_un.S_addr = inet_addr("94.75.229.241");

			if(connect(sv, (sockaddr*)(&svSockAddr), sizeof(svSockAddr))!=0)
			{
				cout << "4" << ErrText(WSAGetLastError()) << endl;		
			}
						
			incs.clSockAddr = &clSockAddr;
			incs.svSockAddr = &svSockAddr;
			incs.cl = &cl;
			incs.sv = &sv;
			
			void* pIncs = &incs;
				
			DWORD threadId1;
			CreateThread(0, 0, cltosv, pIncs, 0, &threadId1);
			
			DWORD threadId2;
			CreateThread(0, 0, svtocl, pIncs, 0, &threadId2);

			while(true) {}
			
			closesocket(cl);
			closesocket(sv);
		}
		else
		{
			// Required version not available
		}

		// Cleanup winsock
		if (WSACleanup()!=0)
		{
			// cleanup failed
		}
	}
	else
	{
		//  startup failed
	}
    return 0;
}

I said it happend in the cltosv function, but I ment that it happend in the svtocl function.

Try to check clSockAddr variable, because an error talks that an address is inaccessible. Maybe port or IP equals 0.

The best solution in this case - debug mode. Place breakpoints and watch the values of variables.

P.S. or maybe firewall blocks incoming connections.

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