1 packet delay with inputstream

I'm writing some code to receive an Inputstream from a node. for this I use a ProcessBuilder which starts up my coap-client to be able to receive the packets.
I buffer all my input. check code below:

Code :

---

 
		command = path + "./coap-client -m GET -p 61616 coap://[aaaa::c30c:0:0:379]/notifications -s 90";
 
			try {
				synchronized(command) {
			        final ProcessBuilder pb = new ProcessBuilder("bash", "-c", command);
			        // merge child's error and normal output streams.
			        // Note it is not called setRedirectErrorStream.
			        pb.redirectErrorStream( true );
 
			        	//p = Runtime.getRuntime().exec(command);
			        p = pb.start();
						System.out.println("process started");
 
					}
 
InputStream is = p.getInputStream();
 
new Thread( new Receiver( is ) ).start();
				try
	            {
					p.waitFor();
	            }
				catch ( InterruptedException e )
	            {
					Thread.currentThread().interrupt();
	            }
 
} catch (IOException e) {
							// TODO Auto-generated catch block
							e.printStackTrace();
						}  finally {}
					}

---

This is my main code. The code that reads out the buffer is listed below:

Code :

---

public void run()
	        {
	    		String line;
	            final BufferedReader br = new BufferedReader( new InputStreamReader( is ), 100); /* keep small for testing */
					line = br.readLine();
				System.out.println(line);
 
	            try {
	            	while ( ( line = br.readLine() ) != null )
	                {
	            		System.out.println( line );
 
	            		line = br.readLine();
	                }
	            br.close();
	            } catch (IOException e) {
	                e.printStackTrace();
	            }
	       }

---

The packages I receive in my buffer are JSON formatted packets. I'm able to display those packets on the eclipse console but they appear with a 1 packet delay.
When I start my program I should immediately get the acknowledge package from the node. But the problem is that I only get my Ack-packet when a new notification has arrived in the buffer... I've looked for delays in the readLine() function but I haven't found any solution yet.

please help me out here...

just possible it may help, do a buffer flush. I assume your delay comes when the buffer is flushed out from the I/O stream. Question are you getting all your data you need its just a delay??

Yes I get all my data but always with a 1 packet delay... so at the start I should get the ACK from my node, but at the moment in my java I get nothing. I tried to debug it and I noticed that my buffer in java was still empty. Only when the second package, a notification is sent from the node, I receive my ACK in my java buffer, and I assume my notification is stuck in the coap-client(written in C) I/O Stream buffer...