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Enable broadcast to reach all subnets #133

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Enable broadcast to reach all subnets #133

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123 changes: 112 additions & 11 deletions src/com/esotericsoftware/kryonet/Client.java
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Original file line number Diff line number Diff line change
Expand Up @@ -455,23 +455,124 @@ private void broadcast (int udpPort, DatagramSocket socket) throws IOException {
dataBuffer.get(data);
for (NetworkInterface iface : Collections.list(NetworkInterface.getNetworkInterfaces())) {
for (InetAddress address : Collections.list(iface.getInetAddresses())) {
// Java 1.5 doesn't support getting the subnet mask, so try the two most common.
byte[] ip = address.getAddress();
ip[3] = -1; // 255.255.255.0
try {
socket.send(new DatagramPacket(data, data.length, InetAddress.getByAddress(ip), udpPort));
} catch (Exception ignored) {
}
ip[2] = -1; // 255.255.0.0
byte[][] allBroadcastByte=allPossibleBroadcastAddrs(address.getAddress());

//All possible subnet masks (based on ip) are used to broadcast
InetAddress[] allBroadcast=new InetAddress[allBroadcastByte.length];
try {
socket.send(new DatagramPacket(data, data.length, InetAddress.getByAddress(ip), udpPort));
} catch (Exception ignored) {
}
for (int i = 0; i < allBroadcast.length; i++) {
socket.send(new DatagramPacket(data, data.length, InetAddress.getByAddress(allBroadcastByte[i]), udpPort));
}
} catch (Exception ignored) {}
}
}
if (DEBUG) debug("kryonet", "Broadcasted host discovery on port: " + udpPort);
}

//Finds all the possible broadcast addresses for a given ipv4 address of the form {byte, byte, byte, byte}
//The highest valued 1 bit is found, and all broadcast addresses from there to 0.0.0.3/30 are returned
private static byte[][] allPossibleBroadcastAddrs(byte[] ip) {
byte[][] output=new byte[][]{};
Vector<byte[]> outputA=new Vector<byte[]>();
int firstOne=firstOne(ip);
switch(firstOne) {
case 0:
outputA.add(new byte[]{-1, -1, -1, -1});
case 1:
outputA.add(new byte[]{(byte)(ip[0]|127), -1, -1, -1});
case 2:
outputA.add(new byte[]{(byte)(ip[0]|63), -1, -1, -1});
case 3:
outputA.add(new byte[]{(byte)(ip[0]|31), -1, -1, -1});
case 4:
outputA.add(new byte[]{(byte)(ip[0]|15), -1, -1, -1});
case 5:
outputA.add(new byte[]{(byte)(ip[0]|7), -1, -1, -1});
case 6:
outputA.add(new byte[]{(byte)(ip[0]|3), -1, -1, -1});
case 7:
outputA.add(new byte[]{(byte)(ip[0]|1), -1, -1, -1});
case 8:
outputA.add(new byte[]{ip[0], -1, -1, -1});
case 9:
outputA.add(new byte[]{ip[0], (byte)(ip[1]|127), -1, -1});
case 10:
outputA.add(new byte[]{ip[0], (byte)(ip[1]|63), -1, -1});
case 11:
outputA.add(new byte[]{ip[0], (byte)(ip[1]|31), -1, -1});
case 12:
outputA.add(new byte[]{ip[0], (byte)(ip[1]|15), -1, -1});
case 13:
outputA.add(new byte[]{ip[0], (byte)(ip[1]|7), -1, -1});
case 14:
outputA.add(new byte[]{ip[0], (byte)(ip[1]|3), -1, -1});
case 15:
outputA.add(new byte[]{ip[0], (byte)(ip[1]|1), -1, -1});
case 16:
outputA.add(new byte[]{ip[0], ip[1], -1, -1});
case 17:
outputA.add(new byte[]{ip[0], ip[1], (byte)(ip[2]|127), -1});
case 18:
outputA.add(new byte[]{ip[0], ip[1], (byte)(ip[2]|63), -1});
case 19:
outputA.add(new byte[]{ip[0], ip[1], (byte)(ip[2]|31), -1});
case 20:
outputA.add(new byte[]{ip[0], ip[1], (byte)(ip[2]|15), -1});
case 21:
outputA.add(new byte[]{ip[0], ip[1], (byte)(ip[2]|7), -1});
case 22:
outputA.add(new byte[]{ip[0], ip[1], (byte)(ip[2]|3), -1});
case 23:
outputA.add(new byte[]{ip[0], ip[1], (byte)(ip[2]|1), -1});
case 24:
outputA.add(new byte[]{ip[0], ip[1], ip[2], -1});
case 25:
outputA.add(new byte[]{ip[0], ip[1], ip[2], (byte)(ip[3]|127)});
case 26:
outputA.add(new byte[]{ip[0], ip[1], ip[2], (byte)(ip[3]|63)});
case 27:
outputA.add(new byte[]{ip[0], ip[1], ip[2], (byte)(ip[3]|31)});
case 28:
outputA.add(new byte[]{ip[0], ip[1], ip[2], (byte)(ip[3]|15)});
case 29:
outputA.add(new byte[]{ip[0], ip[1], ip[2], (byte)(ip[3]|7)});
case 30:
outputA.add(new byte[]{ip[0], ip[1], ip[2], (byte)(ip[3]|3)});
break;
default: //Broadcast address without a subnet mask
outputA.add(new byte[]{-1, -1, -1, -1});
break;
}

output=new byte[outputA.size()][];
int i=0;
for (byte[] addr: outputA) {
output[i]=addr;
i++;
}
return output;
}

//0-indexed from the left. 32 means no 1 bit was found
private static int firstOne(byte[] ip) {
boolean firstOneFound=false;
byte checkedBit=0;
//For each octet until a 1 bit is found...
for (int octet=0; octet<ip.length; octet++) {
//For each bit in that octet until a 1 bit is found...
for (int bit = 0; bit < 8; bit++) {
//Bit shift over to that bit and check if it is 1
if ((byte)(ip[octet] >> 7-bit)==1) {
firstOneFound=true;
}
//If the bit is one, break immediately
if (firstOneFound) break;
checkedBit++;
}
}
return checkedBit;
}

/** Broadcasts a UDP message on the LAN to discover any running servers. The address of the first server to respond is returned.
* @param udpPort The UDP port of the server.
* @param timeoutMillis The number of milliseconds to wait for a response.
Expand Down