UDP packet sent out the wrong interface

I wrote code to proxy UDP packets from a routable subnet to a nonroutable subnet.* Everything works great in the debugger.* I see my packet copied to the nonroutable subnet with a new source IP address.* But when I run the executable outside the debugger it sends the packet out the wrong interface.* It sends it back out the routable subnet.*

This is a sequence of when it works correctly (in debugger).

1. Packet from x.x.x.147 to x.x.x.146 (NIC 1)
2. Copied and sent** 192.168.0.10* to* 192.168.0.20 (NIC 2)

This is a sequence of when it does not work correctly (outside of debugger)

1. Packet from x.x.x.147 to x.x.x.146 (NIC 1)
2. Copied and sent** x.x.x.146* to* 192.168.0.20* (NIC 1)

My code does not change.* Why does it behave different when I'm not running in the debugger?

Code:

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// udpproxy.cpp : main project file.

#include "stdafx.h"

#pragma comment(lib,"ws2_32.lib")
#include<Winsock2.h>
#include<stdio.h>
#include<stdlib.h>
#define BUFFER_LENGTH 1500
#define MAX_PORT_COUNT 20
#define DONT_FRAGMENT false

using namespace System;
using namespace System::Net;
using namespace System::Net::Sockets;

int main(int argc, char *argv[]) {
        WSADATA wsaData;
        Socket ^sSocket;
        int iLen;
        int iSend;
        int iRecv;
        int bytesSent = 0;
        int srvPort = 0;
        int dstPort = 0;
        char recv_buf[BUFFER_LENGTH];
        array<UdpClient^>^ destination = gcnew array<UdpClient^>(MAX_PORT_COUNT);
        int iAddressCount = 0;
        char *address;
        char *srcAddressChar;
        int i = 0;

        struct sockaddr_in ser,cli;

        if (argc < 4) {                  // Test for correct number of parameters
                printf("Usage: UDPProxy <Server Port> <Dest Port> <Dest IP Address>[,<IP Address>,<IP Address>,...] ");
                return -5;
        }
       
        if(WSAStartup(MAKEWORD(2,2),&wsaData)!=0)
        {
                printf("Failed to load Winsock.\n");
                return -1;
        }

        srvPort = atoi(argv[1]);
        printf("--------------------------\n");
        printf("Listening to port %i\n", srvPort);

        dstPort = atoi(argv[2]);
        printf("Forwarding to port %i:\n", dstPort);
       
        printf("Targets:\n");
        address = strtok(argv[3], ",");
        while(address != 0)
        {
                System::String ^dstAddress = gcnew System::String(address);
                destination[iAddressCount] = gcnew UdpClient(dstAddress, dstPort);
                printf("    %s\n", dstAddress);
                iAddressCount++;
                address = strtok(0, ",");
        }
    printf("--------------------------\n");

        UdpClient^ client = gcnew UdpClient();
        client->DontFragment = DONT_FRAGMENT;
       
    Socket^ socket = gcnew Socket(AddressFamily::InterNetwork, SocketType::Dgram, ProtocolType::Udp);
    IPEndPoint^ ipep = gcnew IPEndPoint(IPAddress::Any, srvPort);

    socket->Bind(ipep);

    while(true)
    {
        array<unsigned char>^ message = gcnew array<unsigned char>(BUFFER_LENGTH);
        EndPoint^ Remote = (EndPoint^) gcnew IPEndPoint(IPAddress::Any, 0);

        int recv = socket->ReceiveFrom(message, Remote);
               
                //printf(".");

                for(int i=0; i < iAddressCount; ++i)
                {
                        bytesSent = destination[i]->Send(message, recv);
                        if(bytesSent == recv)
                        {
                                printf(".");
                        }
                }
    }

        WSACleanup();

        return 0;
}

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Your code has nothing to do with this Visual C++ Forum. Nor is it a valid native C++.
If it is something like managed C++ code then please, ask your question in the corresponding Managed C++/CLI forum.

Quote:

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Why does it behave different when I'm not running in the debugger?

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Usually the most probable reason is: your code has some error.