UDP between C# in Unity and a program in C++

Scripting C# & .NET
1

Hi,

I am trying to send data via UDP from a program written in C++ (that I use for tracking) to Unity using .Net in C#. I am kind of lost, all my attempts did not work so far and Unity crashes quite often. Here my code, could anyone tell me were I am wrong ?

Server code in C++

#include <winsock2.h>
#pragma comment(lib, "ws2_32.lib")

int sendUDP()
{
	WSADATA WSAData; //start WSAStartup()
    SOCKET sock; //init socket
    SOCKADDR_IN sin; //infos socket
    WSAStartup(MAKEWORD(2,2), &WSAData); //enable socket use
    sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); //create socket
    sin.sin_addr.s_addr = htonl(INADDR_ANY);
    sin.sin_family = AF_INET; //type socket
    sin.sin_port = htons(28280); //port nb
	char SendBuf[32]="From port 28280";

    while(1)
    {
		sendto(sock, SendBuf, 32, 0, (SOCKADDR *)&sin, sizeof(sin));
    }
	closesocket(sock);
	WSACleanup();
    return 0;
}

Client code C# in Unity

using UnityEngine;
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;

public class capUDP : MonoBehaviour {

static IPEndPoint ep = new IPEndPoint(IPAddress.Any, 0);
static UdpClient udpClient = new UdpClient(28280);
static byte[] receiveBytes = new byte[32]; 
static string returnData = "";
	
	void Start () {
		Thread receiveThread = new Thread(ReceiveData);
        receiveThread.IsBackground = true;
        receiveThread.Start();
	}
	
	void Update () {
		Debug.Log(returnData);
	}
	
	void ReceiveData()
	{
		Debug.Log("receiving...");
		receiveBytes = udpClient.Receive(ref ep); 
		returnData = Encoding.ASCII.GetString(receiveBytes);
	}
}

Thanks,
Gratoo

2

Just two guesses:

In C you should initialize your char-array with 0. It might send whatever is in memory and that might not be ASCII?

Your returnData is used in two threads: one modifies it when something arrives and one prints it. Maybe you should lock() it.

3

Thanks for your reply TobiasS. You were right about the returnData into Update(), it was not a good idea at all :stuck_out_tongue: But to make it work I also changed “htonl(INADDR_ANY);” by “inet_addr(“xxx.xxx.x.xxx”);” in the server code.

So here the working code for the client:

	void Start () {
	}
	
	void Update () {
        receiveThread = new Thread(ReceiveData);
        receiveThread.IsBackground = true;
        receiveThread.Start();
        receiveThread.Abort();
	}
	
	void ReceiveData()
	{
		receiveBytes = udpClient.Receive(ref ep); 
		returnData = Encoding.ASCII.GetString(receiveBytes);
		if(returnData != "") Debug.Log(returnData);
	}

But I guess the code is far from perfect yet, what do you think ? Do I really have to specify my IP ? (I would like my application to run easily on another computer)

Thanks a lot for your help !
Gratoo

4

Hi Gratoo,
I am also working on Unity c# to c++ communication. You have faced the same problem that I am facing now. Did you find the solution. Can you put it here or write an article about it on answers.unity3d.com to help fellow developers.

1 Like