android readLine(); crashes my app
===

i have set a server at an arduino leonardo using an ethernet shield. through a socket connection i can send strings from my android app to my arduino that i can succesfully read. a part of my arduino code is:

    if (client.available() > 0) {
        char thisChar = client.read();
    if (readString.length() < 30){
        readString.concat(thisChar);
        } 
    if (thisChar == '\n') {
        if (readString.indexOf("connect")>0){
            client.print("connection_ok");
        }
        if(readString.indexOf("change")>=0){
            changeLedState();   // set the LED on
        }
       }
    }

while my android code is:

    Socket s = new Socket("192.168.0.177",23);
    PrintWriter out=new PrintWriter(s.getOutputStream(), true);	       
    if (s.isConnected()){		       
         out.println("connect\n");
         BufferedReader r = new BufferedReader(new InputStreamReader(s.getInputStream()));
         String line=r.readLine();
    }



my android app, always crashes at readLine(); if i use out.print ("change"); changeLedState really happens, so i know i can read output strings from my android app, but i have not managed to read the input strings from arduino to android.
anyone can help?