Running an HTTP server in a background thread in Ruby (for use in tests, for example)

server-in-thread-multiple-clients.rb

# serve multiple clients at once
require 'socket'
require 'net/http'

server = TCPServer.new 4040
server_thread = Thread.start do
  loop do
    Thread.start server.accept do |socket|
      /^GET (\S+) HTTP\/1\.1$/ =~ socket.gets.chomp
      path = $1
      sleep 0.5
      socket.print %(HTTP/1.1 200 OK\r\nContent-Type: application/json\r\n\r\n)
      socket.print %({ "path": "#{path}" }\n)
      socket.close
    end
  end
end

# emulate work, such as a test case
%w(/foo /bar /baz).map {|path|
  Thread.start { puts Net::HTTP.get 'localhost', path, 4040 }
}.each(&:join)

# you may want to put this final part in an ensure block
server_thread.exit
server_thread.value
server.close

server-in-thread-single-client.rb

# serve a single client at once
require 'socket'
require 'net/http'

server = TCPServer.new 4040
server_thread = Thread.start do
  while (socket = server.accept) do
    /^GET (\S+) HTTP\/1\.1$/ =~ socket.gets.chomp
    path = $1
    sleep 0.5
    socket.print %(HTTP/1.1 200 OK\r\nContent-Type: application/json\r\n\r\n)
    socket.print %({ "path": "#{path}" }\n)
    socket.close
  end
end

# emulate work, such as a test case
%w(/foo /bar /baz).map {|path|
  Thread.start { puts Net::HTTP.get 'localhost', path, 4040 }
}.each(&:join)

# you may want to put this final part in an ensure block
server_thread.exit
server_thread.value
server.close