StreamCommunication

StreamCommunication is a sample program meant to show how to make programs communicate via stdin and stdout. This is a very cheap and unixy way of writing application plugins.

I got inspired by this year's aichallenge, an online competition for programmers where contendents' provided bots (programs) challenge each other in a virtual arena.

I provide a host written in Java and some bots written in various languages I use.

The host "loads" the bots (spawns two processes with the provided bots) and handle their input and output.

The mighty communication protocol

To keep things simple, the task that the bots have to accomplish (and the protocol used) is very simple. Each protocols responds to 4 "questions": ready?, bye!, generate code and find code.

ready? -> must reply with ready! bye! -> must reply with bye! and exit generate code -> must output 5 lines of each with 5 dots and one randomly placed sharp. Examples of valid codes:

 .....     .....     .....     .....     ...#.
 ...#.     .....     .....     .....     .....
 .....     .....     .....     ..#..     .....
 .....     .#...     .....     .....     .....
 .....     .....     ....#     .....     .....

find code -> must read the following 5 lines from stdin and write the position of the sharp for the provided code (top-left is 0 0). The correct answers for the previous codes are hence: 3 1, 1 3, 4 4, 2 2 and 3 0.

Compiling and running the host

ant compile jar

This creates build/jar/Host.jar. To make to bots communicate, simply provide the commands to launch them, for example:

java -jar build/jar/Host.jar "./cbot" "python pythonbot.py"

runhost.sh and runhost.bat would compile and execute a sample bot for you (if python is installed).

You can experiment with your own bots or take a look at the sample ones I've written (keep reading).

Once executed, Host will output what's going on and any error generated by the bots. Sample output:

Bot 1 ready!
Bot 2 ready!
Generated code:
....#
.....
.....
.....
.....
Bot 2 found the right code [4 0]!
Waving bots goodbye...
Everything went as expected. Good job!

How it all works

The Host program, given two bots as arguments, launches two processes. Let's call them bot1 and bot2. Then:

1. Sends ready? to both bot1 and bot2 and waits for ready! as reply.
2. Sends generate code to bot1 and reads the following 5 lines output by it
3. Checks if that the generated code is valid and finds the position on sharp
4. Sends find code and the five lines of bot1's code to bot2.
5. Reads bots's answer to find code and checks if it matches with what found.
6. Sends bye! to both bot1 and bot2 and waits for bye! in response.

Bots

As a general note, if you launch the bots from withing a script (like in runhost.sh), you may encounter a problem with the bot writing to stdout but its stdout kept from being flushed. To overcome this problem, where possible, I forced the flush of standard output.

I mostly rushed the bots out and my knowledge of the various programming languages I used it varied, so some solution may be more elegant than other (even if I mostly just rewrote the same program over and over trying to include programming languages peculiarities). Feel free to contribute better solutions!

Bash

Plain Unix bash script. Launch it with ./bashbot.sh.

C

Doesn't have any non-standard library dependance. Compile it with gcc cbot.cc -o cbot and launch it with ./cbot.

C++

Doesn't have any non-standard library dependance. Compile it with g++ cppbot.cpp -o cppbot and launch it with ./cppbot.

Clojure

You can launch it with java -cp clojure.jar clojure.main clojurebot.clj or make a Leiningen project and launch it with lein run or compile it as a jar with lein uberjar and use it as a regular jar file.

Coffeescript

This is a one to one port of Node.js script, suffering from the same limitations. See Node.js

Common Lisp

Just run it with clisp clispbot.cl.

CSharp

You can compile it with csc.exe /out:csharpbot.exe csharpbot.cs and simply run it as any .exe file. I haven't tested it with Mono, but it should work out of the box.

FSharp

You can compile it with fsc.exe /out:csharpbot.exe csharpbot.cs and simply run it as any .exe file. I haven't tested it with Mono, but it should work out of the box.

Groovy

Can be run with groovy groovybot.groovy or java groovy.lang.GroovyShell groovybot.groovy.

Haskell

Compile it with ghc -o haskellbot haskellbot.hs or run it with ghc haskellbot.hs.

Java

Compile it with javac JavaBot.java and run it with java JavaBot, as usual.

Lua

Run it with lua luabot.lua

Node.js

This version doesn't work. Because of the asynchronous nature of Node, I couldn't "stop 'n wait" for the output to flush and hence this bot suffers from the flush problem. I've been advised to use the library streamlinejs, but I haven't tried it yet.

Objective C

You can either create a command line XCode solution around the file and just let it compile it, or try to compile it from the cli with gcc main.m -o main -ObjC -framework Foundation.

OCaml

Run it with ocaml ocamlbot.cl.

Perl

Run it with perl perlbot.pl.

PHP

Here I use php as a scripting language, away from its more common web environment. Run it with php phpbot.php

Powershell

This hasn't been tested thoroughly. Microsoft pretends you to register any script before running it or lower the overall security level. Then powershell scripting doesn't work with MS native scripting and couldn't be launched from within the dos batch I was using for testing. I just got bored and stop testing it. The code should work, by the way (if you manage to just run it!).

Python

Run it with python pybot.py.

Racket (Scheme)

Load the file in DrRacket and compile it.

Ruby

Run it with ruby rubybot.rb. Thanks to sort_by { rand } and each_slice(N) this is, I think, the most compact solution.

Scala

Either run it with scala ScalaBot.scala or compile it to a standard java class with scalac ScalaBot.scala.

Tcl

Execute with tclsh tclbot.tcl