Thread: Converting Hex values to IP and Port Number - IP format

Could use some help,

I working on decoding some data from a UDP server. In the response I get a list of IP addresses and Port numbers as a byte array. I then converted them to hex strings.

I'm confused about the format of some of the IP address once I convert them to decimal. Some of them don't seem to follow the normal IP format of xxx.xx.xxx.xx .

Here is the code:

public void addPeer(String addressin, String portin){
        String address = addressin;
        String port = portin;
 
        System.out.println("IP Hex: " + address);
        System.out.println("Port Hex: " + port);
        long A = Long.parseLong(address, 16);
        long B = Long.parseLong(port, 16);
        System.out.println("IP Decimal: " + A);
        System.out.println("Port Decimal: " + B);
 
    }

...and the Output:

IP Hex: 7e7548f3
Port Hex: 969f
IP Decimal: 2121615603
Port Decimal: 38559
 
IP Hex: 6b4da427
Port Hex: 2a97
IP Decimal: 1800250407
Port Decimal: 10903
 
IP Hex: d995a68b
Port Hex: d564
IP Decimal: 3650463371
Port Decimal: 54628
 
IP Hex: 0539728e
Port Hex: 5b39
IP Decimal: 87650958
Port Decimal: 23353

So the 4th one down as Decimal is "87650958"... I'm confused as to what format this is and IP lookup says its not a valid IP.

I don't how that would fit in the format xxx.xx.xxx.xx

Am I converting them wrong or am I just getting junk values from the server?

Thanks for the reply...

I have double checked the data from the UDP reply and it seems to be fine.

Here is the code anyway.

The reply Byte Array goes through a Display method that converts it into a hex string. Then to the passpeer method that pulls out the IP address and Port number and checks for trailing zeros.

passPeers(display(bytereceived));
 
public static String display(byte[] b1) {
        StringBuilder strBuilder = new StringBuilder();
        for(byte val : b1) {
            strBuilder.append(String.format("%02x", val&0xff));
        }
        return strBuilder.toString();
    }
 
    public void passPeers(String received){
        String hold;
        hold = received.substring(40);
        String trim = "";
        int index = 0;
        boolean flip = true;
        String address = "";
        String port = "";
 
 
        if (hold.charAt(index) == '0' && hold.charAt(index + 1) == '0') flip = false;
        while (flip){
            trim = hold.substring(index, index + 12);
            address = trim.substring(0, 8);
            port = trim.substring(8, 12);
            peers.addPeer(addressin, portin);
            index = index + 12;
            if (hold.charAt(index) == '0' && hold.charAt(index + 1) == '0') flip = false;
        }
}

Bellow is the raw data in the bytereceived array...

00000001000000020000068900000000000000195e6eae8beb7f5bb471e42d925bb42fb1b23a54ec236d56c454541f5175e75450f402aa5b512c9c58f38c4f4e905900001fb791956f610539728e5b39027a659f2327c2b11c8b44cabe66468a349db9f204746acdb9955a26c74ba078b9f2e475a0780551000000000000000000000...

Here is a link to the protocol https://www.libtorrent.org/udp_tracker_protocol.html. The above is an announcing reply packet.

The peer list of IP and Port number starts at char(40).

I have this as the output

IP Hex: 5e6eae8b
Port Hex: eb7f
IP Decimal: 1584311947
Port Decimal: 60287
IP Hex: 5bb471e4
Port Hex: 2d92
IP Decimal: 1538552292
Port Decimal: 11666
IP Hex: 5bb42fb1
Port Hex: b23a
IP Decimal: 1538535345
Port Decimal: 45626
IP Hex: 54ec236d
Port Hex: 56c4
IP Decimal: 1424761709
Port Decimal: 22212
IP Hex: 54541f51
Port Hex: 75e7
IP Decimal: 1414799185
Port Decimal: 30183
IP Hex: 5450f402
Port Hex: aa5b
IP Decimal: 1414591490
Port Decimal: 43611
IP Hex: 512c9c58
Port Hex: f38c
IP Decimal: 1361878104
Port Decimal: 62348
IP Hex: 4f4e9059
Port Hex: 0000
IP Decimal: 1330548825
Port Decimal: 0
IP Hex: 1fb79195
Port Hex: 6f61
IP Decimal: 532124053
Port Decimal: 28513
IP Hex: 0539728e
Port Hex: 5b39
IP Decimal: 87650958
Port Decimal: 23353
IP Hex: 027a659f
Port Hex: 2327
IP Decimal: 41575839
Port Decimal: 8999
IP Hex: c2b11c8b
Port Hex: 44ca
IP Decimal: 3266387083
Port Decimal: 17610
IP Hex: be66468a
Port Hex: 349d
IP Decimal: 3194373770
Port Decimal: 13469
IP Hex: b9f20474
Port Hex: 6acd
IP Decimal: 3119645812
Port Decimal: 27341
IP Hex: b9955a26
Port Hex: c74b
IP Decimal: 3113572902
Port Decimal: 51019
IP Hex: a078b9f2
Port Hex: e475
IP Decimal: 2692266482
Port Decimal: 58485
IP Hex: a0780551
Port Hex: 0000
IP Decimal: 2692220241

The error is on the 11th one down... "IP Decimal: 87650958"

Thanks that was it...

What about the port number. Its two bytes long. Would I just convert the two bytes together or bit by bit like the IP?