I program some ad-hoc application on Raspberry PI. I connect PI and my laptop with ad-hoc network and code a little program to test this network. It seem to work if I send a unicast packet between laptop and Raspberry PI via ad-hoc network but I found some weird problem when I send broadcast packet from Raspberry PI to my laptop. The packet wasn't sent from Raspberry PI (I used wireshark to capture packets) However, if I send a broadcast packet from laptop to Raspberry PI, the PI can receive that packet. Moreover If I send a broadcast packet from PI to laptop on local network it work perfectly. I don't know why. Could you please give me some suggestion
wlan0 IEEE 802.11bg ESSID:"AdhocPI" Nickname:"<WIFI@REALTEK>"
Mode:Ad-Hoc Frequency:2.412 GHz Cell: 02:11:87:10:D7:41
Bit Rate:54 Mb/s Sensitivity:0/0
Retry:off RTS thr:off Fragment thr:off
Power Management:off
Link Quality=2/100 Signal level=2/100 Noise level=0/100
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0
lo no wireless extensions.
eth0 no wireless extensions.
This is my ifconfig
eth0 Link encap:Ethernet HWaddr b8:27:eb:b8:30:ad
inet addr:169.254.98.20 Bcast:169.254.255.255 Mask:255.255.0.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:22291 errors:24 dropped:12 overruns:0 frame:12
TX packets:8305 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2187504 (2.0 MiB) TX bytes:1274782 (1.2 MiB)
lo Link encap:Local Loopback
inet addr:127.0.0.1 Mask:255.0.0.0
UP LOOPBACK RUNNING MTU:65536 Metric:1
RX packets:110 errors:0 dropped:0 overruns:0 frame:0
TX packets:110 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:24095 (23.5 KiB) TX bytes:24095 (23.5 KiB)
wlan0 Link encap:Ethernet HWaddr 00:13:ef:80:12:e7
inet addr:192.168.1.103 Bcast:192.168.1.255 Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:1589 errors:0 dropped:1160 overruns:0 frame:0
TX packets:190 errors:0 dropped:11 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:604922 (590.7 KiB) TX bytes:4714 (4.6 KiB)
This is my Java Program to listen a packet
public class UDPServer {
public static void main(String args[]) {
DatagramSocket aSocket = null;
Message replyMsg = new Message(999,"reply");
System.out.println("UDPServer");
try {
aSocket = new DatagramSocket(6669);
aSocket.setBroadcast(true);
while (true) {
byte[] buffer = new byte[1000];
DatagramPacket request = new DatagramPacket(buffer,
buffer.length);
aSocket.receive(request);
Message msgReq = null;
try {
msgReq = (Message)Serializer.deserialize(request.getData());
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Send back to: "+request.getAddress()+ " port "+request.getPort());
byte[]replyBytes = Serializer.serialize(replyMsg);
DatagramPacket reply = new DatagramPacket(replyBytes,
replyBytes.length, request.getAddress(),
request.getPort());
aSocket.send(reply);
System.out.println("Receive Msg : "+ msgReq.show());
}
} catch (SocketException e) {
System.out.println("Socket: " + e.getMessage());
} catch (IOException e) {
System.out.println("IO: " + e.getMessage());
} finally {
if (aSocket != null)
aSocket.close();
}
}
}
This is my Java Program to send a broadcast packet
public class UDPClient {
public static void main(String args[]) {
DatagramSocket aSocket = null;
try {
//System.out.println("UDPClient " +getBroadcast().toString());
aSocket = new DatagramSocket(5008);
Message msgOb = new Message(1, "Hello");
byte[] m = Serializer.serialize(msgOb);
InetAddress aHost = InetAddress.getByName("192.168.1.255");
int serverPort = 6669;
System.out.println("Send data to: "+aHost.getHostAddress()+" Port "+serverPort);
DatagramPacket request = new DatagramPacket(m, m.length,
aHost, serverPort);
aSocket.setBroadcast(true);
System.out.println("Broadcast: "+aSocket.getBroadcast());
aSocket.send(request);
byte[] buffer = new byte[3000];
DatagramPacket reply = new DatagramPacket(buffer, buffer.length);
aSocket.receive(reply);
Message msgRep = null;
try {
msgRep = (Message)Serializer.deserialize(reply.getData());
} catch (ClassNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
System.out.println("Reply: " + msgRep.show());
} catch (SocketException e) {
System.out.println("Socket: " + e.getMessage());
} catch (IOException e) {
System.out.println("IO: " + e.getMessage());
} finally {
if (aSocket != null)aSocket.close();
}
}
The problem is on Wifi-adapter. Just change wifi-adapter which has a driver to support ad-hoc mode. It'll work perfectly.