diff --git a/apps/trx/ctrl_if.py b/apps/trx/ctrl_if.py
new file mode 100644
index 0000000..43fc185
--- /dev/null
+++ b/apps/trx/ctrl_if.py
@@ -0,0 +1,157 @@
+#!/usr/bin/env python2
+# -*- coding: utf-8 -*-
+
+# GR-GSM based transceiver
+# Transceiver UDP interface
+#
+# (C) 2016-2017 by Vadim Yanitskiy <axilirator@gmail.com>
+#
+# All Rights Reserved
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+import socket
+import select
+
+class UDPServer:
+	def __init__(self, remote_addr, remote_port, bind_port):
+		self.sock = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+		self.sock.bind(('0.0.0.0', bind_port))
+		self.sock.setblocking(0)
+
+		# Save remote info
+		self.remote_addr = remote_addr
+		self.remote_port = remote_port
+
+	def loop(self):
+		r_event, w_event, x_event = select.select([self.sock], [], [])
+
+		# Check for incoming data
+		if self.sock in r_event:
+			data, addr = self.sock.recvfrom(128)
+			self.handle_rx(data)
+
+	def shutdown(self):
+		self.sock.close();
+
+	def send(self, data):
+		self.sock.sendto(data, (self.remote_addr, self.remote_port))
+
+	def handle_rx(self, data):
+		raise NotImplementedError
+
+class CTRLInterface(UDPServer):
+	def __init__(self, remote_addr, remote_port, bind_port, radio_if):
+		print("[i] Init TRX CTRL interface")
+		UDPServer.__init__(self, remote_addr, remote_port, bind_port)
+		self.tb = radio_if
+
+	def shutdown(self):
+		print("[i] Shutdown TRX CTRL interface")
+		UDPServer.shutdown(self)
+
+	def handle_rx(self, data):
+		if self.verify_req(data):
+			request = self.prepare_req(data)
+			self.parse_cmd(request)
+		else:
+			print("[!] Wrong data on CTRL interface")
+
+	def verify_req(self, data):
+		# Verify command signature
+		return data.startswith("CMD")
+
+	def prepare_req(self, data):
+		# Strip signature, paddings and \0
+		request = data[4:].strip().strip("\0")
+		# Split into a command and arguments
+		request = request.split(" ")
+		# Now we have something like ["TXTUNE", "941600"]
+		return request
+
+	def verify_cmd(self, request, cmd, argc):
+		# Check if requested command matches
+		if request[0] != cmd:
+			return False
+
+		# And has enough arguments
+		if len(request) - 1 != argc:
+			return False
+
+		# Check if all arguments are numeric
+		for v in request[1:]:
+			if not v.isdigit():
+				return False
+
+		return True
+
+	def parse_cmd(self, request):
+		response_code = "0"
+
+		# Power control
+		if self.verify_cmd(request, "POWERON", 0):
+			print("[i] Recv POWERON cmd")
+			if not self.tb.trx_started:
+				if self.tb.check_available():
+					print("[i] Starting transceiver...")
+					self.tb.trx_started = True
+					self.tb.start()
+				else:
+					print("[!] Transceiver isn't ready to start")
+					response_code = "-1"
+			else:
+				print("[!] Transceiver already started!")
+				response_code = "-1"
+		elif self.verify_cmd(request, "POWEROFF", 0):
+			print("[i] Recv POWEROFF cmd")
+			print("[i] Stopping transceiver...")
+			self.tb.trx_started = False
+			# TODO: flush all buffers between blocks
+			self.tb.stop()
+		elif self.verify_cmd(request, "SETRXGAIN", 1):
+			print("[i] Recv SETRXGAIN cmd")
+			# TODO: check gain value
+			gain = int(request[1])
+			self.tb.set_gain(gain)
+
+		# Tuning Control
+		elif self.verify_cmd(request, "RXTUNE", 1):
+			print("[i] Recv RXTUNE cmd")
+			# TODO: check freq range
+			freq = int(request[1]) * 1000
+			self.tb.set_fc(freq)
+		elif self.verify_cmd(request, "TXTUNE", 1):
+			print("[i] Recv TXTUNE cmd")
+			# TODO: is not implemented yet
+
+		# Misc
+		elif self.verify_cmd(request, "ECHO", 0):
+			print("[i] Recv ECHO cmd")
+
+		# Wrong / unknown command
+		else:
+			print("[!] Wrong request on CTRL interface")
+			response_code = "-1"
+
+		# Anyway, we need to respond
+		self.send_response(request, response_code)
+
+	def send_response(self, request, response_code):
+		# Include status code, for example ["TXTUNE", "0", "941600"]
+		request.insert(1, response_code)
+		# Add the response signature, and join back to string
+		response = "RSP " + " ".join(request) + "\0"
+		# Now we have something like "RSP TXTUNE 0 941600"
+		self.send(response)