udp - Where is the error // why doesn't it work? (Java Chat program) -

i wanted write udp java chat program can send , receive messages , person using program. figured out socket programming own (google search etc.), don't understand every single part. basic idea read random ip want chat string, converting ip , starting 2 threads, 1 sending messages port , 1 receiving messages @ port b (the threads used being both able send , recieve messages @ same time). every thread has it's own class. far, good. both classes have method run both in big try-catch block. @ 2 catch blocks, added several error messages, first "test123" , "test456" can understand happens when. when compiling code, can type in ip (i tried localhost testing). when type in message, should recieve message "chat partner sent: ", instead don't anything. both threads in infinite loop, when force program terminate (by pressing ctrl+c (i run .class via command)), error message "test123" before program terminates. questions are: why don't receive message , why program throw "test123" when force program terminate? errors? in advance helping. here's code:

import java.net.*; import java.util.scanner;  public class chat {     static inetaddress ip;     static int sport=11111;     static int rport=11112;     public static void main(string[] args) throws exception{         system.out.println("zu welcher ip soll verbunden werden?");//"which ip want connect with?"         scanner sc = new scanner(system.in);         string ipraw=sc.next(); //type in ip address string         ip=inetaddress.getbyname(ipraw); //converting string real ip address         thread sender = new sender();         sender.start(); //start sending thread         thread receiver = new receiver();         receiver.start(); //start receiving thread     } } class sender extends thread{     public void run(){         byte[] senddata = new byte[1024];         scanner scantext = new scanner(system.in);         try{             datagramsocket socket = new datagramsocket();             while(true){                 string textsend = scantext.next();                 senddata = textsend.getbytes();                 datagrampacket out = new datagrampacket(senddata, senddata.length, chat.ip, chat.rport);                 socket.send(out);             }         }         catch(exception e){         system.out.println("test123");         }     } }  class receiver extends thread{     public void run(){         byte[] receivedata = new byte[1024];         try{             datagramsocket socket = new datagramsocket();             while(true){                 datagrampacket in = new datagrampacket(receivedata, receivedata.length, chat.ip, chat.sport);                 socket.receive(in);                 string message = new string(in.getdata());                 system.out.println("chatpartner sagt: " + message);//"partner said <message>"                        }         }         catch(exception e){         system.out.println("test456");         }     } } 

the sender thread wating insert data on system.in (just type something). blocked here, on line: string textsend = scantext.next();