Java UDP

[homer56]

Hallo zusammen


Hab ein kleines Problem mit dem übermitteln per UDP. Der Client versucht immer die ganzen 1024 Bytes anzuzeigen.


Server:


import java.net.*;
import java.io.*;

class UDPServer
{
public static void main(String[] args)
{
byte [] buffer = new byte[1024];
String myMessage ;

try
{
// Create a Datagram Socket
DatagramSocket socket = new DatagramSocket(Integer.parseInt(args[0]));

// Create an empty Datagram Packet
DatagramPacket packet = new DatagramPacket(buffer, buffer.length );

// receive request from client and get client info
socket.receive(packet);
InetAddress client = packet.getAddress();
int client_port = packet.getPort();
System.out.println(" Received "+new String(buffer)+" from "+client);

// send some data to the client
myMessage = "Angekommen!";
buffer = myMessage.getBytes("US-ASCII") ;
packet = new DatagramPacket(buffer, buffer.length, client, client_port);
socket.send(packet);
}
catch(UnknownHostException e){ System.out.println(e); }
catch(IOException e){ System.out.println(e); }
}
}



Client:


import java.net.*;
import java.io.*;

class UDPClient {

public static void main (String args []) {

byte [] buffer = new byte[1024];
String host = "127.0.0.1";
int port = 666; // default: local echo service

//host = args[0];
//port = Integer.parseInt(args[1]);

try{
// Create a Datagram Socket
DatagramSocket socket = new DatagramSocket();

// Create a packet with server information
InetAddress server = InetAddress.getByName(host);
DatagramPacket packet = new DatagramPacket(buffer, buffer.length, server, port);


// Send the packet
socket.send(packet);

// receive request from client and get client info
packet = new DatagramPacket(buffer, buffer.length);
socket.receive(packet);

//InetAddress client = packet.getAddress();
//int client_port = packet.getPort();
System.out.println(new String(buffer));
}
catch(UnknownHostException e){ System.out.println(e); }
catch(IOException e){ System.out.println(e); }
}
}



Die Ausgabe vom Client:


Angekommen![][][][][][][][].....


Ausgabe vom Server:


Received[][][][][][][][][][].....


[] wird so lange angezeigt bis die 1024 Bytes verbraucht sind.


Die Rot hervorgehobenen Stellen werden wohl die Schuldigen sein, aber ich finde irgendwie nicht heraus was ich anderst machen soll.

[homer56]

Ok, bisschen selber denken schadet nie. :rolleyes:


Client:


import java.net.*;
import java.io.*;

class UDPClient {

public static void main (String args []) {

byte [] buffer = new byte[1024];
String host = "127.0.0.1";
int port = 666; // default: local echo service

//host = args[0];
//port = Integer.parseInt(args[1]);

try{
// Create a Datagram Socket
DatagramSocket socket = new DatagramSocket();

// Create a packet with server information

String myMessage = "Antworte mir!!!!!!!!!";
buffer = myMessage.getBytes("US-ASCII");

InetAddress server = InetAddress.getByName(host);
DatagramPacket packet = new DatagramPacket(buffer, buffer.length, server, port);

// Send the packet
socket.send(packet);
buffer = new byte[1024];
// receive request from client and get client info
packet = new DatagramPacket(buffer, buffer.length);
socket.receive(packet);


// output of the data from server
System.out.println(new String(buffer).trim());

}
catch(UnknownHostException e){ System.out.println(e); }
catch(IOException e){ System.out.println(e); }
}
}

[homer56]

Guten Tag


Hab nun mal das Ganze in Klassen und Methoden verpackt. Nun bekomme ich einen Fehler wo ich nicht wirklich weiss wo ich ihn suchen muss.


Code:


//************************************************** ****//
// usage: java UDPClient port
//************************************************** ****//

import java.net.*;
import java.io.*;

class UDPClient {
public static void main (String args []) {

networkStuff connection1 = new networkStuff();
connection1.setOptionsAndSendPacket(7, "127.0.0.1");
connection1.recivePacket();
}
}


class networkStuff{

protected byte [] buffer = new byte[1024];
protected DatagramPacket packet;
protected DatagramSocket socket;

void setOptionsAndSendPacket(int port, String host){
try{
// Create a Datagram Socket
DatagramSocket socket = new DatagramSocket();

// Create a packet with server information
String myMessage = "Sende Request!";
buffer = myMessage.getBytes("US-ASCII");

// Set host and port
InetAddress server = InetAddress.getByName(host);
DatagramPacket packet = new DatagramPacket(buffer, buffer.length, server, port);

// Send the packet and reset the buffer
socket.send(packet);
buffer = new byte[1024];
}

catch(UnknownHostException e){ System.out.println(e); }
catch(IOException e){ System.out.println(e); }
}

void recivePacket(){

// receive request from client and get client info
try {
packet = new DatagramPacket(buffer, buffer.length);
socket.receive(packet);

// output the data from the server
System.out.println(new String(buffer).trim());
}
catch (IOException e) {System.out.println(e);}
}
}


Fehler beim Starten:


java.lang.NullPointerException
at networkStuff.recivePacket(UDPClient.java:51)
at UDPClient.main(UDPClient.java:13)
Exception in thread "main"


Wäre echt super wenn mir jemand nen Tipp geben könnte.


Edit:


private InetAddress server;

private DatagramSocket socket;

private DatagramPacket packet;

Hinzufügen bringt den gleichen Fehler. :(

[anda_skoa]

Der Backtrace sagt dir doch eh die Zeile.

socket dürfte null sein, vermutlich deswegen, weil nie eine Zusweisung auf diese Variable passiert (zumindest nicht im geposteten Code)

Vermutung: die lokale Variable socket in setOptionsAndSendPacket sollte vermutlich die Variable der Instanz sein

Ciao,
_