Question

I’m having trouble getting a socket connection between Android(client) and a c# app(server) to read a response correctly.

I’ve successfully got a message sending from android to c#, and I’m reading it fine on that end. But when I try to send an acknowledgement back to android, I don’t know the correct way to handle this, and I’ve had to make some assumptions where tutorials have been unclear. I am getting a response back in android, but it’s not 100% correct. I’ve verified via Wireshark that c# is sending what I want it to send, and the text looks fine until it gets to android.

C#:
    public void SendClientMessage()
    {
        NetworkStream clientStream = _Client.GetStream();
        ASCIIEncoding encoder = new ASCIIEncoding();
        byte[] buffer = encoder.GetBytes("Hello Client!");  //Static test message

        clientStream.Write(buffer, 0, buffer.Length);
        clientStream.Flush();
    }

…

Android:
    private void listenResponse()
    {
        Log.i(TAG, "listenRespose() Listening...");
        try
        {
           InputStream is = socket.getInputStream();
           BufferedInputStream bis = new BufferedInputStream(is);
           byte[] buffer = new byte[1024];
           int countBytesRead = bis.read(buffer, 0, 8);
           String response = new String(buffer);
           Log.i(TAG, "listenResponse() Heard: " + response);
        }
        catch (IOException e)
        {
           Log.e(TAG, "listenResponse() IOException", e);
           e.printStackTrace();
        }
        Log.i(TAG, "listenResponse() Done Listening.");
    }

…

WireShark shows:
    Hello Client!

…

Android LogCat shows:
    listenRespose() Listening...
    listenResponse() Heard: Hello Cl??????????????????????????? [... ?s continue for a long time]
    listenResponse() Done Listening.

If instead I initialize my String like this:

String response = new String(buffer, 0, countBytesRead);

I don’t get all the question marks at least, but I still don’t get the full string I should be getting. Am I initializing my byte[] wrong, or is there a different way to do this better suited for plain text?

Answer 1

You only read 8 bytes here

int countBytesRead = bis.read(buffer, 0, 8);
//                     max bytes to read ^

instead, read all you can:

int countBytesRead = bis.read(buffer, 0, Buffer.length);

The question marks you see are because your buffer is not initialized.