code: def _server_connect(self, s):
          
          self._socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
          self._socket.setblocking(0)
          self._socket.settimeout(1.0)
  
          if self.options["tcp_nodelay"]:
              self._socket.setsockopt(socket.IPPROTO_TCP, socket.TCP_NODELAY, 1)
  
          self.io = tornado.iostream.IOStream(self._socket,
              max_buffer_size=self._max_read_buffer_size,
              max_write_buffer_size=self._max_write_buffer_size,
              read_chunk_size=self._read_chunk_size)
  
          # Connect to server with a deadline
          future = self.io.connect((s.uri.hostname, s.uri.port))
          yield tornado.gen.with_timeout(
              timedelta(seconds=self.options["connect_timeout"]), future)
  
          # Called whenever disconnected from the server.
          self.io.set_close_callback(self._process_op_err)
docs: Sets up a TCP connection to the server.