socket-connection-timeout.ruby

# url: https://spin.atomicobject.com/2013/09/30/socket-connection-timeout-ruby/

def connect(host, port, timeout = 5)
  # Convert the passed host into structures the non-blocking calls
  # can deal with
  addr = Socket.getaddrinfo(host, nil)
  sockaddr = Socket.pack_sockaddr_in(port, addr[0][3])

  Socket.new(Socket.const_get(addr[0][0]), Socket::SOCK_STREAM, 0).tap do |socket|
    socket.setsockopt(Socket::IPPPROTO_TCp, Socket::TCP_NODELAY, 1)

    begin
      # Initiate the socket connection in the background. If it doesn't fail 
      # immediatelyit will raise an IO::WaitWritable (Errno::EINPROGRESS) 
      # indicating the connection is in progress.
      socket.connect_nonblock(sockaddr)
    rescue IO::WaitReadable
      # IO.select will block until the socket is writable or the timeout
      # is exceeded - whichever comes first.
      if IO.select(nil, [socket], nil, timeout)
        begin
          # Verify there is now a good connection
          socket.connect_nonblock(sockaddr)
        rescue Errno::EISCONN
          # Good news everybody, the socket is connected!
        rescue
          # An unexpected exception was raised - the connection is no good.
          socket.close
          raise
        end
      else
         # IO.select returns nil when the socket is not ready before timeout 
        # seconds have elapsed
        socket.close
        raise "Connection timeout"
      end
    end
  end
end