Ruby IO from a service at port 6557 in Sinatra

Question

I have to take a dump of a service in sinatra and display it in the content area of the webpage.

The Service I have to access via code runs on server at port 6557. It doesnt use any encryption or authentication. Its a plain readonly request response thingy like http. Here is what works in teminal

$ echo "GET hosts" | nc 192.168.1.1 6557

gives me the intended output. I need to do something similar using the sinatra application.

I wrote this code but is grossly incorrect. Can sombody help me with code or lookup materials or examples.

get '/' do
        host = "192.168.1.1"
        port = 6557
        dat = ""
        @socket = TCPSocket.open (host, port)
                while(true)
                        if(IO.select([],[],[@socket],0))
                                socket.close
                                return
                        end
                        begin
                                while( (data = @socket.recv_nonblock(100)) != "")
                                        dat = dat+ data
                                end
                                rescue Errno::EAGAIN
                        end
                        begin
                                @str = "GET hosts"
                                @socket.puts(@str);
                        rescue Errno::EAGAIN
                        rescue EOFError
                                exit
                        end
                        IO.select([@socket], [@socket], [@socket])
                end
        @line = dat
        erb :info
end

The code on execution just hangs up. Also if possible please give some links to read up to get a conceptual context of the problem.

Answer 1

You can execute shell commands directly from ruby using backticks or the system command. Something like this may work for you:

get "/" do
  @line = `echo "GET hosts" | nc 192.168.1.1 6557`
  erb :info
end

Check out the ruby docs for Kernel#system for more info.

Answer 2

I think the Ruby equivalent to your shell command should be as simple as:

require "socket"

socket = TCPSocket.new "192.168.1.1", 6557
socket.puts "GET hosts"
socket.read

According to the docs, #read should close the socket automatically, so you don't need to worry about doing that manually.