diff --git a/src/osmo_gsm_tester/esme.py b/src/osmo_gsm_tester/esme.py
new file mode 100644
index 0000000..f92863d
--- /dev/null
+++ b/src/osmo_gsm_tester/esme.py
@@ -0,0 +1,138 @@
+# osmo_gsm_tester: SMPP ESME to talk to SMSC
+#
+# Copyright (C) 2017 by sysmocom - s.f.m.c. GmbH
+#
+# Author: Pau Espin Pedrol <pespin@sysmocom.de>
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as
+# published by the Free Software Foundation, either version 3 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 Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import smpplib.gsm
+import smpplib.client
+import smpplib.consts
+import smpplib.exceptions
+
+from . import log, util, event_loop, sms
+
+# if you want to know what's happening inside python-smpplib
+#import logging
+#logging.basicConfig(level='DEBUG')
+
+MAX_SYS_ID_LEN = 16
+MAX_PASSWD_LEN = 16
+
+class Esme(log.Origin):
+    client = None
+    smsc = None
+
+    def __init__(self, msisdn):
+        self.msisdn = msisdn
+        # Get last characters of msisdn to stay inside MAX_SYS_ID_LEN. Similar to modulus operator.
+        self.set_system_id('esme-' + self.msisdn[-11:])
+        super().__init__(log.C_TST, self.system_id)
+        self.set_password('esme-pwd')
+        self.connected = False
+        self.bound = False
+        self.listening = False
+
+    def __del__(self):
+        try:
+            self.disconnect()
+        except smpplib.exceptions.ConnectionError:
+            pass
+
+    def set_smsc(self, smsc):
+        self.smsc = smsc
+
+    def set_system_id(self, name):
+        if len(name) > MAX_SYS_ID_LEN:
+            raise log.Error('Esme system_id too long! %d vs %d', len(name), MAX_SYS_ID_LEN)
+        self.system_id = name
+
+    def set_password(self, password):
+        if len(password) > MAX_PASSWD_LEN:
+            raise log.Error('Esme password too long! %d vs %d', len(password), MAX_PASSWD_LEN)
+        self.password = password
+
+    def conf_for_smsc(self):
+        config = { 'system_id': self.system_id, 'password': self.password }
+        return config
+
+    def poll(self):
+        self.client.poll()
+
+    def start_listening(self):
+        self.listening = True
+        event_loop.register_poll_func(self.poll)
+
+    def stop_listening(self):
+        if not self.listening:
+            return
+        self.listening = False
+        # Empty the queue before processing the unbind + disconnect PDUs
+        event_loop.unregister_poll_func(self.poll)
+        self.poll()
+
+    def connect(self):
+        host, port = self.smsc.addr_port
+        if self.client:
+            self.disconnect()
+        self.client = smpplib.client.Client(host, port, timeout=None)
+        self.client.set_message_sent_handler(
+            lambda pdu: self.dbg('message sent:', repr(pdu)) )
+        self.client.set_message_received_handler(
+            lambda pdu: self.dbg('message received:', repr(pdu)) )
+        self.client.connect()
+        self.connected = True
+        self.client.bind_transceiver(system_id=self.system_id, password=self.password)
+        self.bound = True
+        self.log('Connected and bound successfully. Starting to listen')
+        self.start_listening()
+
+    def disconnect(self):
+        self.stop_listening()
+        if self.bound:
+            self.client.unbind()
+            self.bound = False
+        if self.connected:
+            self.client.disconnect()
+            self.connected = False
+
+    def run_method_expect_failure(self, errcode, method, *args):
+        try:
+            method(*args)
+            #it should not succeed, raise an exception:
+            raise log.Error('SMPP Failure: %s should have failed with SMPP error %d (%s) but succeeded.' % (method, errcode, smpplib.consts.DESCRIPTIONS[errcode]))
+        except smpplib.exceptions.PDUError as e:
+            if e.args[1] != errcode:
+                raise e
+
+    def sms_send(self, sms_obj):
+        parts, encoding_flag, msg_type_flag = smpplib.gsm.make_parts(str(sms_obj))
+
+        self.log('Sending SMS "%s" to %s' % (str(sms_obj), sms_obj.dst_msisdn()))
+        for part in parts:
+            pdu = self.client.send_message(
+                source_addr_ton=smpplib.consts.SMPP_TON_INTL,
+                source_addr_npi=smpplib.consts.SMPP_NPI_ISDN,
+                source_addr=sms_obj.src_msisdn(),
+                dest_addr_ton=smpplib.consts.SMPP_TON_INTL,
+                dest_addr_npi=smpplib.consts.SMPP_NPI_ISDN,
+                destination_addr=sms_obj.dst_msisdn(),
+                short_message=part,
+                data_coding=encoding_flag,
+                esm_class=smpplib.consts.SMPP_MSGMODE_FORWARD,
+                registered_delivery=False,
+                )
+
+# vim: expandtab tabstop=4 shiftwidth=4