I am working on a application on MEGACO protocol on Controller side. I am sending MEGACO messages to the Media Gateway via UDP prptocol. And the Media gateway is answering the requests. When I run wireshark with specified port and IP filter wireshark shows all the captured MEGACO packets. But in my application (written in JAVA) some of the packets are not reaching. More specifically saying to my application only Transaction Reply and Transaction Reply Acknowledgement (Reference: RFC 3015) messages are not reaching.
I have tried a lot of permutations and combinations. Even I have allocated new Datagram Packet and buffer space for each receiving messages as test. But no result. My code for the udp receiver is following.
while (running) {
//do work here
try {
byte[] dpBuffer = new byte[MAX_BUFFER_SIZE];
DatagramPacket dp = new DatagramPacket(dpBuffer, MAX_BUFFER_SIZE);
this.socket.receive(dp);
byte[] temp = new byte[dp.getLength()];
System.arraycopy(dp.getData(), 0, temp, 0, dp.getLength());
System.out.println("Read data");
for(int i=0;i<temp.length;i++)
{
System.out.print((char)(temp[i]));
}
ByteArrayUtil msg = new ByteArrayUtil(temp, dp.getLength());
msgParser.parseMsg(msg);
} catch (Exception e) {
logger.error("Megaco Reader Failed to read Packet due to :" ,e);
}
}
Any help??
THanks E_net4.
As I have mentioned in my comment, I was using wrong filter in wireshark. in wireshark if you use only
"udp.port == x"
as the filter it will filter those packets having either source or destination port x. To filter those packets that have either source port == x or destination port ==x, you should use udp.srcport == x and udp.destport==xrespectively.
Thanks everyone.
Related
It's my first post so it may be not well stylished but I tried...
So... I have two machines, both running Java. I want them to run something like this.
Client: sends multicast to listening servers.
Server(s): the server captures the multicast and sends a unicast back with name of local machine that server runs on.
Client: receives the unicast with the server adress(es) and makes a list with their hostnames.
But the client doesn't even send the multicast (I was watching wireshark capturing packets)
It only sends something when I put 230.0.0.1 as multicast address, but then, the server doesn't receive the packet.
EDIT: When I send a unicast packet to the server it responds fine.
Here is my code:
try
{
//The client runs on LeJOS EV3 so I used their classes a bit
LCDOutputStream lcd = new LCDOutputStream();
PrintStream p = new PrintStream(lcd);
while(true)
{
if(Button.waitForAnyPress() == Button.ID_ESCAPE)
{
break;
}
byte[] buf = this.writeString("get_ip");
DatagramSocket sender = new DatagramSocket();
DatagramPacket packet = new DatagramPacket(buf, buf.length, InetAddress.getByName("230.0.0.1"), 5555);
sender.send(packet);
sender.close();
p.println("Sent Multicast");
}
p.close();
lcd.close();
}
catch(Exception e)
{
console.printException(e);
}
Here is the server code:
MulticastSocket s = new MulticastSocket(5555);
s.joinGroup(InetAddress.getByName("225.1.1.1"));
while(true)
{
try
{
/*
* 225.1.100.1
*
DataSender.Impl.reply("225.1.100.1", 5555, InetAddress.getLocalHost().getHostName(), "get_ip");*/
byte[] buf = new byte[256];
DatagramPacket p = new DatagramPacket(buf, buf.length);
s.receive(p);
System.out.println("DEBUG: received request");
}
catch(IOException e)
{
e.printStackTrace();
break;
}
}
s.close();
The comments made by ecle in response to the following post helped me resolve a similar issue: Java Multicast sample program is unable to deliver packets within LAN (across hosts). In my case, adding setInterface(<server address>); worked. For example:
MulticastSocket s = new MulticastSocket(5555);
s.setInterface(<server address>);
s.joinGroup(InetAddress.getByName("225.1.1.1"));
I've written a basic udp client server where one android sends message to the server and server relays it to the rest of the clients.
The issue is, the incoming udp messages get to the server and server relays them back but they never reach the rest of the devices.
Whats really amazing is that if I use the server as echo server (i.e relaying only to sender) then everything works. All client and server sockets use same port 2706
Server code
while (true) {
DatagramPacket packetToReceive = new DatagramPacket(new byte[2048], 2048);
try {
listenerSocket.receive(packetToReceive);
InetAddress senderAddress = packetToReceive.getAddress();
relayedBytes += packetToReceive.getLength();
if (!connectedClients.contains(senderAddress)) {
connectedClients.add(senderAddress);
}
for (InetAddress addr : connectedClients) {
// commenting this line will make it an echo server
if (!addr.equals(senderAddress))
{
//The following actually prints the ips of the android
//devices so it knows where to send
System.out.println(senderAddress.getHostAddress().toString() +
" to " + addr.getHostAddress().toString());
byte[] data = packetToReceive.getData();
packetToReceive.setData(data, 0, packetToReceive.getLength());
packetToReceive.setAddress(addr);
listenerSocket.send(packetToReceive);
}
}
} catch (IOException) {
e.printStackTrace();
}
}
android sender logic:
mainSocket=new DatagramSocket(homePort);
//targetAddressString is the public IP of server
target = InetAddress.getByName(targetAddressString);
while (true) {
byte[] data = getdata();
if (data == null)
continue;
DatagramPacket packet = new DatagramPacket(data, data.length, target, targetPort);
mainSocket.send(packet);
}
meanwhile on other thread the reciever just waits with the same udp socket:
while (true) {
Log.d("Player", "Waiting for data");
DatagramPacket packet = new DatagramPacket(new byte[2048], 2048);
try {
mainSocket.receive(packet);
Log.d("Player", "packet received");
//do something with the packet
} catch (IOException e) {
e.printStackTrace();
}
}
It never moves further than waiting for data since it'll block until it receives a packet
Moreover I can also see it in the wifi and Mobile data icons that no data is ever received but data sending is always on and is seen received on the server
**EDIT:- Echo server **
while (true) {
DatagramPacket receivedPacket = new DatagramPacket(new byte[2048], 2048);
try {
listenerSocket.receive(receivedPacket);
InetAddress senderAddress = receivedPacket.getAddress();
if (!connectedClients.contains(senderAddress)) {
connectedClients.add(senderAddress);
}
for (InetAddress addr : connectedClients) {
byte[] data = receivedPacket.getData();
DatagramPacket sendPacket= new DatagramPacket(data, 0, receivedPacket.getLength(), addr, receivedPacket.getPort());
listenerSocket.send(sendPacket);
}
} catch (IOException e) {
// ...
}
}
Basically it should relay the message to every single client who've ever sent any data but somehow it only sends its to its original sender the rest of clients miss it. the code is trolling with me
This is the NAT traversal problem as you have figured out.
Here's a few hints:
The server can be hardcoded to listen on port 2706. But it shouldn't make any assumptions about what source port of received packets are. From your code, it doesn't look like you ever attempt to call setPort. So even if the NAT wasn't mapping your port number differently, I'm not sure how your original code was even getting the any destination port set. But I think you figured this out based on your own answer and your updated code.
Don't hardcode a client port on the client's socket. Choose port "0" (or don't set one) on your socket to let the OS choose the first available port for you. If you have multiple clients behind the same NAT, this behavior will allow for quicker client restarts, multiple devices behind the same NAT, and other nice things.
Holly Molly! I finally figured it out , it was my own fault I wasn't considering my cellphone provider's Nat and was assuming 2706 port in public IP as well.
Turns out actually I was under my cellphone network's NAT and my port 2706 was converted to some hideous port number by the time it reached the server. So I had to consider the port no of the actual packet received rather than the one set on the phone.
In a nutshell it was like this
cellphone (port 2706)-> NAT (port 40234) -> Server (port 40234)
and so I was actually trying to send back data to 2706 instead of 40234 -_-'
Once I start to send back the packets at 40234 (or whatever came with the packet) instead of 2706 , it gracefully followed the path back to my android cellphone and everything was fine.
I am trying to write a very simple SSDP discovery routine for a certain UPnP-enabled TV. Here is a stripped-down version of my code:
private void discover() {
String header = "M-SEARCH * HTTP/1.1";
String[][] fields = new String[][] {
{"ST", "ssdp:all"},
{"MAN", "\"ssdp:discover\""},
{"HOST", "239.255.255.250:1900"},
{"MX", "10"}};
String p=this.make_packet(header, fields);
MulticastSocket s = null;
ArrayList<String> devices=new ArrayList<String>();
String[] ret;
String[] loc;
try {
InetAddress addr=InetAddress.getByName("239.255.255.250");
s = new MulticastSocket(1900);
s.setReuseAddress(true);
s.setSoTimeout(3000);
s.joinGroup(addr);
DatagramPacket pack=new DatagramPacket(p.getBytes("UTF-8"), p.length(), addr, 1900);
s.send(pack);
byte[] buffer=new byte[1024];
DatagramPacket packrec=new DatagramPacket(buffer, 1024);
for(;;) {
System.out.println("Waiting for response...");
s.receive(packrec);
System.out.println(new String(buffer, 0, packrec.getLength()));
}
} catch (Exception e) {
System.out.println(e);
}
}
I compile and run the code on a Win8 machine via console. The socket always received exactly one response: a 1:1 copy of the message to be sent. This is probably correct, I guess, since the socket joins the multicast group in the beginning. However, no other UPnP devices reply, although I can see them in 3rd party UPnP inspectors.
When watching the network traffic with WireShark, no package seems to get sent by my code at all, although no exception is thrown. When scanning the network with a different UPnP inspector from the same machine, outbound packages are logged in WireShark (although oddly the replies of some devices are not, even though the inspector finds them).
I am messing around with this for four days now, but to no avail. Any ideas?
Thanks,
Eric
P.S.: JDK 1.8.0_45 (64bit)
I'm facing a very weird problem with receiving data using UDP in Android.
I'm writing an application to control a wifi module from an android device. I'm able to successfully send data to this remote wifi device. But I'm not able to receive 'complete' data packet from this wifi device.
My code in android is:
public static void receivePacket(int receiverPort, Context context) {
DatagramSocket socket = null;
String text = "";
try {
byte[] message = new byte[1500];
DatagramPacket packet = new DatagramPacket(message, message.length);
socket = new DatagramSocket(receiverPort);
//socket.setSoTimeout(5000);
for (int i = 0; i < 12; i++) {
socket.receive(packet);
text += new String(message, 0, packet.getLength()) + "\n";
}
socket.close();
Log.d("Received Message", text);
} catch (Exception e) {
Log.e("UDP", "S: Error", e);
} finally {
if(null != socket){
socket.close();
}
}
}
So if I'm expecting the data "$BEG1;$PID2;$PIP192.168.15.245;$PPN80;$DAT987654321;$END1;" I'm only getting "$BEG1;$PID2;$PIP192.168.15.245;$PPN80;$DAT98"
I tried to use UDP WinChat application to see if it's able to get the message from the wifi module and I'm able to get the entire data.
Also if i try sending a really long message to the android device using UDP Win Chat Application I'm able to get the entire data!
I'm totally confused! Please Help.
I was able to isolate the problem. (Still havent found the fix though :(...)
From the above code I'm making use of the same packet.getLength() for every iteration assuming that it will change each time according to the data it has received. But sadly that's not the expected behavior. The getLength() makes use of the previous value and truncates the newly arrived messages.
[Please note: This is a random behavior and doesn't happen all the time]
Now the question is, how do I change or refresh this attribute everytime I receive a new message within the loop?
You need to reset the DatagramPacket length before every receive. Otherwise it keeps shrinking to the smallest packet received so far.
I'm attempting to use Java Datagrams to create a packet stream between server and client. The problem is that, although I receive confirmation that packets are being sent, they are all lost before they reach the client listener I set up. I have it right now so that there's a timeout after 5 seconds, which happens every time I run it.
class DGServer extends Thread
{
private DatagramSocket server;
public DGServer() throws IOException
{
server = new DatagramSocket();
}
public void run()
{
try
{
server.connect(App.Local, 4200);
System.out.println("Server starting...");
int i = 0;
while (server.isConnected() && (i < 256))
{
byte[] buffer = new byte[1];
buffer[0] = (byte) ++i;
DatagramPacket packet = new DatagramPacket(buffer, buffer.length, App.Local, 4200);
System.out.println("Sedning " + i + " to client...");
server.send(packet);
Thread.sleep(500);
}
}
catch (Exception e)
{
e.printStackTrace();
}
System.out.println("Server Finished!");
if (! server.isClosed())
server.close();
}
}
class DGClient extends Thread
{
private DatagramSocket client;
public DGClient() throws SocketException
{
client = new DatagramSocket();
}
public void run()
{
try
{
client.connect(App.Local, 4200);
client.setSoTimeout(5000);
System.out.println("Client starting...");
int i = 0;
while (client.isConnected() && (i < 256))
{
byte[] buffer = new byte[1];
DatagramPacket packet;
packet = new DatagramPacket(buffer, 1, App.Local, 4200);
//System.out.println("Sedning " + i + " to server...");
client.receive(packet);
buffer = packet.getData();
System.out.println("Client Received:\t" + packet.getData()[0]);
Thread.sleep(500);
}
}
catch (Exception e)
{
e.printStackTrace();
}
System.out.println("Client Finished!");
if (! client.isClosed())
client.close();
}
}
You may choose to skim over the second class. They're widely the same, it just replaces server.send, with client.receive. Also, this class was not designed to really do anything important. So, a lot of the code(like, Exception handling), is written very simplistically.
Is there anything I can do to prevent the loss of packets? I have the port forwarded on my computer(not that it should matter, I'm using my localhost, which is App.Local in case you wondered).
Also, side question. I originally had it set up as a single class, coded to send a packet, then turn around and receive one. But it threw an exception because the 'ICMP Port is unreachable'. Does anyone know why this happens?
Ok first off, I think you are testing both the server and the client at the same time, so you don't have any idea whether which one fails.
You should use either netcat (nc) or wireshark to test the client
with netcat, you can run the following command
nc -l -u -p 4200 -vv
This will tell netcat to listen (-l) on udp (-u) on port (-p 4200) and be very verbose (-vv)
This way you'll be able to check if your client can connect to anything.
You can use the same program to check if your server can receive connections from a known working program with
nc -u [target ip] 4200
There is a netcat cheatsheet here
You can also check netcat to netcat to diagnose if it is purely a network issue. Maybe the firewalls/NAT aren't configured correctly
Why both server and client doing a connect ?
Shouldn't one side be sending the data ?
Something like :
DatagramSocket socket = new DatagramSocket();
DatagramPacket packet = new DatagramPacket(buf, buf.length,
address, 4200);
socket.send(packet);
It sounds to me like there is some packet filter / firewall interfering with UDP traffic between the client and server on the port that you are using. It could be simple packet filtering, it could be NAT (which interferes with UDP traffic unless you take special steps), it could be some accidental network misconfiguration.
But it threw an exception because the 'ICMP Port is unreachable'. Does anyone know why this happens?
IMO, this is more evidence of packet filtering.
(However, its also a bit unexpected that you should receive this in response to trying to sent a datagram. I'd simply expect there to be no response at all, and any ICMP responses to a UDP request to have been dropped on the floor by the OS. But, I may be wrong about this ...
Now if you were using a regular stream socket; e.g. TCP/IP, this behaviour would be understandable.)
You're not binding the sending socket to a specific port number, so the client won't be able to send to it if connected. I suspect you have the same problem in reverse as well, i.e. the client socket isn't bound to port 4200. That would explain everything.
I would get rid of the connects and use explicit port numbers when sending, and the incoming port number when replying.
I am sure you are aware that UDP is a lossy proocol and you have allowed for this. Still you should expect to get some packets.
I suggest you test whether your program works by using the client and server on the same host and on different hosts, avoiding any firewalls. If this works then you have a network configuration issue.
If you are running both of them in the same machine this is never going to work because you are connecting both (server and client) to the same port.