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I seriously dun have much knowledge about UDP broadcast.
I looked over some examples over the internet for it, but they went way over my head.
What i need to do is create UDP broadcast connection, send and recieve packets.
Plus also ping some URL's or IP addresses.
Can anyone provide a solution?
A good example would be considered!
Getting the Broadcast Address
You need to access the wifi manager to get the DHCP info and construct a broadcast address from that:
InetAddress getBroadcastAddress() throws IOException {
WifiManager wifi = mContext.getSystemService(Context.WIFI_SERVICE);
DhcpInfo dhcp = wifi.getDhcpInfo();
// handle null somehow
int broadcast = (dhcp.ipAddress & dhcp.netmask) | ~dhcp.netmask;
byte[] quads = new byte[4];
for (int k = 0; k < 4; k++)
quads[k] = (byte) ((broadcast >> k * 8) & 0xFF);
return InetAddress.getByAddress(quads);
}
Sending and Receiving UDP Broadcast Packets
Having constructed the broadcast address, things work as normal. The following code would send the string data over broadcast and then wait for a response:
DatagramSocket socket = new DatagramSocket(PORT);
socket.setBroadcast(true);
DatagramPacket packet = new DatagramPacket(data.getBytes(), data.length(),
getBroadcastAddress(), DISCOVERY_PORT);
socket.send(packet);
byte[] buf = new byte[1024];
DatagramPacket packet = new DatagramPacket(buf, buf.length);
socket.receive(packet);
Source: http://code.google.com/p/boxeeremote/downloads/list
http://www.helloandroid.com/tutorials/simple-udp-communication-example
http://sourcecodemania.com/udp-datagram-sockets-in-java/
Related
This code works with this address "228.5.6.7", but not with this one "FF7E:230::1234" (devices used: Samsung S4 & TabA).
// join a Multicast group and send the group salutations
String msg = "Hello";
InetAddress group = InetAddress.getByName("228.5.6.7");
MulticastSocket s = new MulticastSocket(6789);
s.joinGroup(group);
DatagramPacket hi = new DatagramPacket(msg.getBytes(), msg.length(), group, 6789);
s.send(hi);
// get their responses!
byte[] buf = new byte[1000];
DatagramPacket recv = new DatagramPacket(buf, buf.length);
s.receive(recv);
// OK, I'm done talking - leave the group...
s.leaveGroup(group);
I tried this example too, it gave me the same result.
Impossible to know if the problem happens when the group is joined or when the DatagramPacket is sent.
I intend to create an Android app that should discover computers on LAN. I tried to use ping the broadcast address. I've got two problems:
The determined broadcast address differs in Windows and on Android. Android tells me 10.255.255.255, http://www.remotemonitoringsystems.ca/broadcast.php tells me 10.111.111.255.
When I try to use the broadcast from command prompt, I get no result on any of the 2 addresses
In Android, I use the following code to determine the address:
InetAddress getBroadcastAddress()
{
try
{
WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
DhcpInfo dhcp = wifi.getDhcpInfo();
// handle null somehow
int broadcast = (dhcp.ipAddress & dhcp.netmask) | ~dhcp.netmask;
byte[] quads = new byte[4];
for (int k = 0; k < 4; k++)
quads[k] = (byte) ((broadcast >> k * 8) & 0xFF);
return InetAddress.getByAddress(quads);
}
catch (Exception e)
{
e.printStackTrace();
}
return null;
}
What address should I use? Why can't I get any ping from computers on the LAN? How should I determine the existing computers on the LAN?
The approach was wrong.
Instead of pinging every existing computer, I should use the broadcast address to send out a specific message and receive reply from the computers that can read and understand that message.
That's how I eventually accomplished the task.
In my application I'd like to get all the IP addresses that are taken by computers in the LAN using the broadcast address. I used the following code to determine the broadcast address.
InetAddress getBroadcastAddress()
{
try
{
WifiManager wifi = (WifiManager) getSystemService(Context.WIFI_SERVICE);
DhcpInfo dhcp = wifi.getDhcpInfo();
// handle null somehow
int broadcast = (dhcp.ipAddress & dhcp.netmask) | ~dhcp.netmask;
byte[] quads = new byte[4];
for (int k = 0; k < 4; k++)
quads[k] = (byte) ((broadcast >> k * 8) & 0xFF);
return InetAddress.getByAddress(quads);
}
catch (Exception e)
{
e.printStackTrace();
}
return null;
}
Now that I have it, as far as I know, when one uses the broadcast address, every computer answers it, so if I simply send a "ping" message to that address, the computers of the LAN will answer it. How should I ping them in Android? What command would send me the taken addresses?
The following code simply returns the packet from the sending phone but I need the computers' addresses:
int PORT = 8080;
int DISCOVERY_PORT = 8080;
try
{
DatagramSocket socket = new DatagramSocket(PORT);
socket.setBroadcast(true);
String data="TEST";
DatagramPacket packet = new DatagramPacket(data.getBytes(), data.length(),
getBroadcastAddress(), DISCOVERY_PORT);
socket.send(packet);
byte[] buf = new byte[1024];
DatagramPacket packet2 = new DatagramPacket(buf, buf.length);
Log.w(Tags.DEBUG,"Receive start");
socket.receive(packet2);
Log.w(Tags.DEBUG,packet2.getAddress().toString());
}
catch (Exception e)
{
e.printStackTrace();
}
Is it even possible?
EDIT:
If I'm honest it works as it is written: my phone sends an UDP packet and my phone receives the incoming packages. As the only package is coming from my phone, it is obvious that the address is my phone's address. However, if the broadcast address is valid, each network interface should send the signal back. Am I correct?
You are partially correct.
When you send a UDP packet to a broadcast address, all the computers on the network will receive the packet, unless a router on the network restricts UDP packets being sent to the broadcast address. This is mostly the case on a corporate network.
But not all computers will reply to that packet, they need to know what to do with it.
Either you write a server application that understands your UDP packet and is configured to reply to that packet and deploy that server application to all of the computers on the network.
Or you implement an existing discovery protocol such as Bonjour (Mac) or SSDP (Windows)
I suggest you take a look at ZeroConf Service Discovery if you want to use existing protocols rather then deploying your own application.
http://en.wikipedia.org/wiki/Zero-configuration_networking#Service_discovery
I hope this explanation helps you with your problem.
I want to receive mpegts over udp in my android application. I am using gstreamer for that. Right now, I am trying to send the mpegts stream from vlc player from the same computer over udp.
In my android application, I am giving the uri udp://10.0.2.2:1234 but the application gives error Could not get/set settings from/on resource. I have tried to get solutions from internet, but no luck so far.
1) UDP address range is from 224.0.0.0 to 239.255.255.255, so you cannot use 10.x.x.x
2) After you deal with adresses, refer to this link to deal with programmatic part:
Getting the Broadcast Address You need to access the wifi manager to get the DHCP info and construct a broadcast address from that:
InetAddress getBroadcastAddress() throws IOException {
WifiManager wifi = mContext.getSystemService(Context.WIFI_SERVICE);
DhcpInfo dhcp = wifi.getDhcpInfo();
// handle null somehow
int broadcast = (dhcp.ipAddress & dhcp.netmask) | ~dhcp.netmask;
byte[] quads = new byte[4];
for (int k = 0; k < 4; k++)
quads[k] = (byte) ((broadcast >> k * 8) & 0xFF);
return InetAddress.getByAddress(quads);
}
Sending and Receiving UDP Broadcast Packets Having constructed the broadcast address, things work as normal. The following code would
send the string data over broadcast and then wait for a response:
DatagramSocket socket = new DatagramSocket(PORT);
socket.setBroadcast(true);
DatagramPacket packet = new DatagramPacket(data.getBytes(), data.length(),
getBroadcastAddress(), DISCOVERY_PORT);
socket.send(packet);
byte[] buf = new byte[1024];
DatagramPacket packet = new DatagramPacket(buf, buf.length);
socket.receive(packet);
I am experiencing a problem on Android when sending SIP packets over UDP to the port 5060 using a device instead of the emulator. The exception is:
java.net.SocketException: sendto failed: EPERM(Opereation not permitted)
On some devices such as the Galaxy Nexus the same code works bot on other devices such as the Asus Transformer TF101 and the Galaxy Tab 2 I am experiencing these problems. I have the required permission android.permission.INTERNET. When sending the same SIP packet over another port (say 9876) the packet is sent successfully. Even when sending other content over port 5060 (not SIP packets) the packet is still sent successfully. It seems that the combination of SIP packets over port 5060 are not being permitted on some devices. I created a test program to replicate this problem:
try
{
DatagramSocket clientSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName("10.111.110.6");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String sentence = "Register sip ...";
sendData = sentence.getBytes();
DatagramPacket sendPacket = new DatagramPacket(sendData,
sendData.length, IPAddress, 5060);
clientSocket.send(sendPacket);
DatagramPacket receivePacket = new DatagramPacket(receiveData,
receiveData.length);
clientSocket.receive(receivePacket);
int x = receivePacket.getLength();
String modifiedSentence = new String(receivePacket.getData(), 0, x);
ds_tv.setText("FROM SERVER:" + modifiedSentence + " Length: "+ x);
clientSocket.close();
}
catch (Exception e)
{
Log.e("Test", e.getMessage());
ds_tv.setText(e.getMessage());
}
This test program consists just of a single button and the above code is called in its onClick() event. The packet consisting of the String sentence which contains the SIP registration packet is not sent over port 5060. If I modify the port, the packet is sent successfully and even if I modify the content of the string sentence. However if I send the SIP registration packet over port 5060 the SocketException occurs. I do not know what could be the problem or how to go about solving such an issue.
The problem has been solved and the error was being caused from the payload of the SIP packet. The CSeq value in the SIP packet was being set to 0 initially. Instead it had to start from 1.