Question

I have a Java application which is Voip. I am using the one socket to send and receive information at the same time via threads. Code is shown below ..

Socket clientSocket = sockList.accept();
OutputStream outSock = clientSocket.getOutputStream();
InputStream inSock = clientSocket.getInputStream();
new Thread( new Capture(outSock)).start();
new Thread( new PlayAudio(inSock)).start();
outSock.close();
clientSocket.close();

The problem that I’m finding is that when I write to the outputstream, it blocks on the first write. I’m sending not many bytes. Bellow is my write code.

private class Capture implements Runnable{

    private OutputStream out;
    public Capture(OutputStream out){
        this.out = out;
    }
    @Override
    public void run() {
        try{
            int numBytesRead;
            TargetDataLine outLine = getMic();
            outLine.open();
            outLine.start();

            byte[] data = new byte[outLine.getBufferSize() / 5];
            byte[] test = {0x1,0x1,0x1};

            while(true) {       
                //numBytesRead =  outLine.read(data, 0, data.length);
                //System.out.println(numBytesRead);
                out.write(test, 0, test.length);
                out.flush();
                /*if(numBytesRead > 0){
                    out.write(data, 0, data.length);
                    System.out.println("C");
                }*/
            }
        }catch(Exception ex){}
    }
}

The other thread that reads the sound code is …

private class PlayAudio implements Runnable{

    private InputStream in;
    public PlayAudio(InputStream in){
        this.in = in;
    }
    @Override
    public void run() {
        int write;
        try{
        SourceDataLine inLine = getSpeaker();
        inLine.open();
        inLine.start();
        byte[] data = new byte[inLine.getBufferSize()];
        byte[] test = new byte[3];
        while(true){
            System.out.println(1);
            //write = in.read(data, 0, data.length);
            in.read(test, 0 , test.length);
            System.out.println(2);
            /*if(write > 0){
                inLine.write(data, 0, write);
                System.out.println(3);
                System.out.println(write);
            }*/
        }
        } catch(Exception ex){}
    }

}

I’ve commented a good portion of the actual code since I’m just trying to get it to work. My write function blocks indefinitely on the first write. Is it possible this could be a problem with my threads? My only thought is that the output and input streams are sharing my socket object which may cause a deadlock or something. Please let me know whats up.

Answer 1

Yes you can write to a sockets input and output stream at the same time.

from do-java-sockets-support-full-duplex

Since the input stream and the output stream are separate objects within the Socket, the only thing you might concern yourself with is, what happens if you had 2 threads trying to read or write (two threads, same input/output stream) at the same time? The read/write methods of the InputStream/OutputStream classes are not synchronized. It is possible, however, that if you’re using a sub-class of InputStream/OutputStream, that the reading/writing methods you’re calling are synchronized. You can check the javadoc for whatever class/methods you’re calling, and find that out pretty quick.