Sending packets over TCP server

[Zsdfhdfgasdf Gsfgsdgsdgsd]

I'm making a TCP server in Ruby, and I still haven't figured out how I
can send packets the way it should be sent. I know how to receive
packets and such though...

For example, one of the packets I need to send looks like this:

Packet ID: 0x00
Purpose: Server Identification: Response to a joining player. The user
type indicates whether a player is an operator (0x64) or not (0x00.)
Current protocol version is 0x07.

Fields:
Packet ID Byte
Protocol Version Byte
Server name String
Server MOTD String
User Type Byte



The code I'm using for the server looks like this:

inform "Starting server"
server = TCPServer.new('127.0.0.1', config['port'])

--------------------
while true #Runs all the time, or until user chooses to quit.
Thread.start(server.accept) do |client|
data = client.recv(1024)
data = data.split(" ")
inform "Recieved Player identification from #{data[0]}"
client.write "#{config['name']} #{config['motd']}"
sleep 60
end
end
--------------------

While it outputs "<Thu Jul 15 18:16:18 +0200 2010> Recieved Player
identification from "(name)"

The client side says that it's been disconnected.

I believe it's because I'm sending data wrong. May someone correct me or
give me pointers?

 

[Brian Candler]

I'm making a TCP server in Ruby, and I still haven't figured out how I
can send packets the way it should be sent. I know how to receive
packets and such though...

For example, one of the packets I need to send looks like this:

Packet ID: 0x00
Purpose: Server Identification: Response to a joining player. The user
type indicates whether a player is an operator (0x64) or not (0x00.)
Current protocol version is 0x07.

Fields:
Packet ID Byte
Protocol Version Byte
Server name String
Server MOTD String
User Type Byte

You need more detail than that. Is a string of a fixed size, or
terminated by a null, or prefixed by a length byte, or something else?

You can send raw data just by sticking the bytes a string, like this:

client.write "\x00\x07foobar\x00baz\x07"

For building such strings, Array#pack and String#unpack are going to be
what you're looking for.

[0,7,"foobar","baz",100].pack("CCZ*Z*C")

=> "\000\afoobar\000baz\000d"

 

[Zsdfhdfgasdf Gsfgsdgsdgsd]

client.write "\x00\x07foobar\x00baz\x07"

I didn't know that we could just "escape" characters like that to make
it a byte.

Thanks for that information
(Gawd, I'm so dumb. Why is it so hard to find this stuff?)

 

[Zsdfhdfgasdf Gsfgsdgsdgsd]

Also, if a string DOES contain bytes, it won't show.

 

[Brian Candler]

I didn't know that we could just "escape" characters like that to make
it a byte.

http://ruby-doc.org/docs/ProgrammingRuby/

Navigate to chapter "The Ruby Language" in top-left box. Scroll down to
the section headed "Strings", and see the inset box "Substitutions in
double-quoted strings"

(Gawd, I'm so dumb. Why is it so hard to find this stuff?)

The hard part is finding it the first time. It's easy to find it again


Regards,

Brian.

 

[Brian Candler]

Also, if a string DOES contain bytes, it won't show.

a = "\x07\x00\x41\x42\x43\xff"
puts "Returns: #{a.inspect}"
puts "Returns: #{a.unpack("H*").first}"

How would I manipulate it?

Just as a String:

a.length
a[1,3] # slice from pos 1 for 3 bytes
.. etc

But if you know precisely the format you're expecting, then
String#unpack will allow you to break it up into integers and
substrings.

 

[Zsdfhdfgasdf Gsfgsdgsdgsd]

Amazing! Then again, thank you. I think I finally reached the point
where I can make this server without opening another Google query!