#!/usr/bin/ruby

# this is a TCP proxy which dumps the transmitted data in hex on stdout
# (c) Yoann Guillot 2009, license: wtfpl v2

require 'socket'
require 'enumerator'

class String
def hexdump(fmt=nil, ctx={})
	fmt ||= ['c', 'd', 'a']
	ctx[:pos] ||= 0
	ctx[:lastline] ||= []
	ctx[:lastdup]
	unpack('C*').each_slice(16) { |s|
		if s != ctx[:lastline]
			ctx[:lastdup] = false
			print '%04x  ' % ctx[:pos]
			print s.map { |b| '%02x' % b }.join(' ').ljust(3*16-1) + '  ' if fmt.include? 'c'
			print s.pack('C*').unpack('L*').map { |bb| '%08x' % bb }.join(' ').ljust(9*4-1) + '  ' if fmt.include? 'd'
			print s.map { |c| (32..126).include?(c) ? c : ?. }.pack('C*') if fmt.include? 'a'
			puts
		elsif not ctx[:lastdup]
			ctx[:lastdup] = true
			puts '*'
		end
		ctx[:lastline] = s
		ctx[:pos] += s.length
	}
	puts '%04x' % ctx[:pos] if not ctx[:noend]
end
end

def bouncepkt(clt, srv, timeout=nil)
	s2c = ''
	c2s = ''
	loop do
		break if not IO.select([clt, srv], nil, nil, timeout)

		while s2c.length < 1024*16 and IO.select([srv], nil, nil, 0)
			str = (srv.read(1) rescue nil)
			break if not str or str.empty?
			s2c << str
		end

		while c2s.length < 1024*16 and IO.select([clt], nil, nil, 0)
			str = (clt.read(1) rescue nil)
			break if not str or str.empty?
			c2s << str
		end

		if s2c.length > 0 and IO.select(nil, [clt], nil, 0)
			puts 's -> c'
			s2c.hexdump(['c', 'a'])
			clt.write s2c
			s2c.replace ''
		end

		if c2s.length > 0 and IO.select(nil, [srv], nil, 0)
			puts 'c -> s'
			c2s.hexdump(['c', 'a'])
			srv.write c2s
			c2s.replace ''
		end
	end
end


if $0 == __FILE__
if ARGV.length < 4
	abort "usage: bnc <lhost> <lport> <rhost> <rport> [<timeout_ms>]"
end

lhost = ARGV.shift
lport = Integer(ARGV.shift)
rhost = ARGV.shift
rport = Integer(ARGV.shift)
timeout = Integer(ARGV.shift) if not ARGV.empty?

s = TCPServer.new(lhost, lport)

loop do
	puts "waiting..."
	a = s.accept
	puts "incoming connection"
	c = TCPSocket.new(rhost, rport)
	
	begin
		bouncepkt(a, c, timeout)
	rescue SystemCallError
	end

	puts "connection closed"
	a.close
	c.close
end
end