diff --git a/library/OPCAP_Adapter.ttcn b/library/OPCAP_Adapter.ttcn
new file mode 100644
index 0000000..8bcc3fd
--- /dev/null
+++ b/library/OPCAP_Adapter.ttcn
@@ -0,0 +1,105 @@
+module OPCAP_Adapter {
+
+/* OPCAP Adapter layer, sitting on top of OPCAP_CodecPort.
+ * test suites can 'inherit' in order to have a OPCAP connection to the IUT which they're testing
+ *
+ * (C) 2021 by Harald Welte <laforge@gnumonks.org>
+ * All rights reserved.
+ *
+ * Released under the terms of GNU General Public License, Version 2 or
+ * (at your option) any later version.
+ */
+
+
+import from Osmocom_Types all;
+import from General_Types all;
+import from OPCAP_Types all;
+import from OPCAP_Templates all;
+import from OPCAP_CodecPort all;
+import from OPCAP_CodecPort_CtrlFunct all;
+import from IPL4asp_Types all;
+import from IPL4asp_PortType all;
+import from Socket_API_Definitions all;
+
+const integer NUM_OPCAP := 3;
+
+type component OPCAP_Adapter_CT {
+	/* down-facing port to OPCAP Codec port */
+	port OPCAP_CODEC_PT OPCAP[NUM_OPCAP];
+	var IPL4asp_Types.ConnectionId g_opcap_conn_id[NUM_OPCAP] := { -1, -1, -1 };
+}
+
+private function f_set_tcp_segmentation(integer idx) runs on OPCAP_Adapter_CT {
+	/* Set function for dissecting the binary stream into packets */
+	var f_IPL4_getMsgLen vl_f := refers(f_IPL4_fixedMsgLen);
+	/* Offset: 2, size of length: 2, delta: 4, multiplier: 1, big-endian */
+	OPCAP_CodecPort_CtrlFunct.f_IPL4_setGetMsgLen(OPCAP[idx], g_opcap_conn_id[idx], vl_f, {2, 2, 4, 1, 0});
+}
+
+function f_connect(charstring remote_host, IPL4asp_Types.PortNumber remote_port,
+		   charstring local_host, IPL4asp_Types.PortNumber local_port, integer idx := 0)
+runs on OPCAP_Adapter_CT {
+	var IPL4asp_Types.Result res;
+	map(self:OPCAP[idx], system:OPCAP);
+	if (g_opcap_conn_id[idx] != -1) {
+		OPCAP_CodecPort_CtrlFunct.f_IPL4_close(OPCAP[idx], g_opcap_conn_id[idx], {tcp := {}});
+		g_opcap_conn_id[idx] := -1;
+	}
+	res := OPCAP_CodecPort_CtrlFunct.f_IPL4_connect(OPCAP[idx], remote_host, remote_port,
+							local_host, local_port, 0, { tcp :={} });
+	if (not ispresent(res.connId)) {
+		setverdict(fail, "Could not connect to OPCAP port, check your configuration ",
+			"{remote ", remote_host, ":", remote_port, " local ", local_host, ":", local_port, "}");
+		mtc.stop;
+	}
+	g_opcap_conn_id[idx] := res.connId;
+
+	f_set_tcp_segmentation(idx);
+}
+
+/* Function to use to bind to a local port as IPA server, accepting remote clients */
+function f_bind(charstring local_host, IPL4asp_Types.PortNumber local_port, integer idx := 0)
+runs on OPCAP_Adapter_CT {
+	var IPL4asp_Types.Result res;
+	map(self:OPCAP[idx], system:OPCAP);
+	if (g_opcap_conn_id[idx] != -1) {
+		OPCAP_CodecPort_CtrlFunct.f_IPL4_close(OPCAP[idx], g_opcap_conn_id[idx], {tcp := {}});
+		g_opcap_conn_id[idx] := -1;
+	}
+	res := OPCAP_CodecPort_CtrlFunct.f_IPL4_listen(OPCAP[idx], local_host, local_port, { tcp:={} });
+	if (not ispresent(res.connId)) {
+		setverdict(fail, "Could not bind to OPCAP port, check your configuration ",
+			   "{local ", local_host, ":", local_port, "}");
+		mtc.stop;
+	}
+	g_opcap_conn_id[idx] := res.connId;
+
+	f_set_tcp_segmentation(idx);
+}
+
+function f_wait_client_connect(integer idx) runs on OPCAP_Adapter_CT {
+	var IPL4asp_Types.PortEvent rx_event;
+	OPCAP[idx].receive(IPL4asp_Types.PortEvent:{connOpened:=?}) -> value rx_event {
+		log("Connection from ", rx_event.connOpened.remName, ":", rx_event.connOpened.remPort);
+		/* we want to store the client's connId, not the 'bind socket' one */
+		g_opcap_conn_id[idx] := rx_event.connOpened.connId;
+	}
+}
+
+function f_disconnect(integer idx) runs on OPCAP_Adapter_CT {
+	OPCAP_CodecPort_CtrlFunct.f_IPL4_close(OPCAP[idx], g_opcap_conn_id[idx], {tcp := {}});
+	OPCAP[idx].clear;
+};
+
+function f_opcap_send(template (value) OPCAP_PDU pdu, integer idx := 0) runs on OPCAP_Adapter_CT {
+	OPCAP[idx].send(ts_OPCAP_Send(g_opcap_conn_id[idx], pdu));
+}
+
+function f_opcap_exp(template OPCAP_PDU exp, integer idx := 0) runs on OPCAP_Adapter_CT return OPCAP_PDU {
+	var OPCAP_RecvFrom rf;
+	OPCAP[idx].receive(tr_OPCAP_Recv(g_opcap_conn_id[idx], exp)) -> value rf;
+	return rf.msg;
+}
+
+
+}