Send message from one program to another in Unity

Question

I have two different executable files running on same computer which has Windows OS. Both of them are build in Unity. I want to send message from one to other without using network.

How do you send message from an exe program to another exe program in Unity?

Is this possible with integrated Mono/.net functionality or something else?

Answer 1

You can use Named Pipes which uses shared memory to communicate with another application on the-same machine.

Go to File --> Build Settings... select PC, Mac & Linux Standalone then click on Player Settings.... Now, change Api Compatibility Level to .NET 2.0.

Close and re-open Visual Studio. Now, you can import using System.IO.Pipes; and be able to use NamedPipeServerStream and NamedPipeClientStream.

Below is a very simplified server and client. You must do that in a Thread and should also handle exception.

If you don't want to use Thread, there is also asynchronous parameter (PipeOptions.Asynchronous) that makes it a non blocking operator. It gets complicated from there and you have to look for some examples for that on MS doc.

Simple Server:

//Create Server Instance
NamedPipeServerStream server = new NamedPipeServerStream("MyCOMApp", PipeDirection.InOut, 1);
//Wait for a client to connect
server.WaitForConnection();
//Created stream for reading and writing
StreamString serverStream = new StreamString(server);
//Send Message to Client
serverStream.WriteString("Hello From Server");
//Read from Client
string dataFromClient = serverStream.ReadString();
UnityEngine.Debug.Log("Received from Client: " + dataFromClient);
//Close Connection
server.Close();

Simple Client:

//Create Client Instance
NamedPipeClientStream client = new NamedPipeClientStream(".", "MyCOMApp",
               PipeDirection.InOut, PipeOptions.None,
               TokenImpersonationLevel.Impersonation);

//Connect to server
client.Connect();
//Created stream for reading and writing
StreamString clientStream = new StreamString(client);
//Read from Server
string dataFromServer = clientStream.ReadString();
UnityEngine.Debug.Log("Received from Server: " + dataFromServer);
//Send Message to Server
clientStream.WriteString("Bye from client");
//Close client
client.Close();

The StreamString class from MS Doc:

public class StreamString
{
    private Stream ioStream;
    private UnicodeEncoding streamEncoding;

    public StreamString(Stream ioStream)
    {
        this.ioStream = ioStream;
        streamEncoding = new UnicodeEncoding();
    }

    public string ReadString()
    {
        int len = 0;

        len = ioStream.ReadByte() * 256;
        len += ioStream.ReadByte();
        byte[] inBuffer = new byte[len];
        ioStream.Read(inBuffer, 0, len);

        return streamEncoding.GetString(inBuffer);
    }

    public int WriteString(string outString)
    {
        byte[] outBuffer = streamEncoding.GetBytes(outString);
        int len = outBuffer.Length;
        if (len > UInt16.MaxValue)
        {
            len = (int)UInt16.MaxValue;
        }
        ioStream.WriteByte((byte)(len / 256));
        ioStream.WriteByte((byte)(len & 255));
        ioStream.Write(outBuffer, 0, len);
        ioStream.Flush();

        return outBuffer.Length + 2;
    }
}

Answer 2

You could have a file they both write and read to. You can put a timestamp with it to show when the last message was written