Question

I have the following code in C#:

Console.WriteLine("Connecting to server...");
TcpClient client = new TcpClient("127.0.0.1", 25565);
client.Client.Send(BitConverter.GetBytes(0x02));
client.Client.Send(BitConverter.GetBytes(0x0005));
client.Client.Send(Encoding.UTF8.GetBytes("wedtm"));
Console.Write("{0:x2}", client.GetStream().ReadByte());

For the life of me, I can’t figure out how to transpose this to ruby. Any help here?

This is what I have so far, but it’s not working as expected:

require 'socket'
s = TCPSocket.open("127.0.0.1", 25565)
s.write(0x02)
s.write(0x0005)
s.write("wedtm".bytes)
response = s.recvfrom(2)
puts "Response Size #{response.size}: #{response.to_s}"

The response should be 0x02

EDIT:

I’m assuming I have to use String#unpack on this, however, I can’t figure out how to get “wedtm” to output to the appropriate \x000\x000\x000\x000 format.

Answer 1

There are at least two things to consider here:

1. Network byte order is big-endian. This means that you should always think in single bytes or arrays of bytes, as bytes are not subject to being shuffled around while larger types are.
2. C#’s BitConverter.GetBytes(int16) returns 2 bytes in little-endian format and GetBytes(int32) returns 4 bytes in little-endian format

Without knowing any Ruby or its string format, I’d guess you need to do something like this for the first part:

s.write("\x02\x00".bytes)
s.write("\x05\x00\x00\x00".bytes)

The second part should be okay.

WireShark is an invaluable tool when debugging network code and/or reverse engineering networking protocols, record the traffic of the C# app and compare the difference with yours.