There is a server that responds to requests on a socket. The client has functions to emit requests and functions to handle responses from the server.

The problem is that the request sending function and the response handling function are two unrelated functions. Given a server response X, how can I know whether it's a response to request X or some other request Y?

I would like to make a construct that would ensure that response X is definitely the answer to request X and also to make a function requestX() that returns response X and not some other response Y.

This question is mostly about the general programming approach and not about any specific language construct. Preferably, though, the answer would involve Ruby, TCP sockets, and PHP.

My code so far:

require 'socket'

class TheConnection
    def initialize(config)
        @config = config
    end
    def send(s)
        toConsole("--> #{s}")
        @conn.send "#{s}\n", 0 
    end
    def connect()
        # Connect to the server
        begin
            @conn = TCPSocket.open(@config['server'], @config['port'])
        rescue Interrupt
        rescue Exception => detail
            toConsole('Exception: ' + detail.message())
            print detail.backtrace.join('\n')
            retry
        end
    end
    def getSpecificAnswer(input)
        send "GET #{input}"
    end
    def handle_server_input(s)
        case s.strip
            when /^Hello. (.*)$/i
                toConsole "[ Server says hello ]"
                send "Hello to you too! #{$1}"              
            else
                toConsole(s)
        end
    end
    def main_loop()
        while true
            ready = select([@conn, $stdin], nil, nil, nil)
            next if !ready
            for s in ready[0]
                if s == $stdin then
                    return if $stdin.eof
                    s = $stdin.gets
                    send s
                elsif s == @conn then
                    return if @conn.eof
                    s = @conn.gets
                    handle_server_input(s)
                end
            end
        end
    end
    def toConsole(msg)
        t = Time.new
        puts t.strftime("[%H:%M:%S]") + ' ' + msg
    end
end
@config = Hash[
    'server'=>'test.server.com',
    'port'=>'2020'
]
$conn = TheConnection.new(@config)
$conn.connect()
$conn.getSpecificAnswer('itemsX')

begin
    $conn.main_loop()
rescue Interrupt
rescue Exception => detail
    $conn.toConsole('Exception: ' + detail.message())
    print detail.backtrace.join('\n')
    retry
end