Dear all,
OK, so now the plot thickens; among the registered websocket subprotocols
(https://www.iana.org/assignments/websocket/websocket.xml) we have also the popular IoT protocol MQTT.
On the below link one can find a list of public MQTT over WebSocket brokers that can be used for testing:
https://github.com/mqtt/mqtt.github.io/wiki/public_brokers
Not all of them are functional all the time though.
Apacho Apollo used previously also exposes a Websocket interface presenting MQTT service.
As MQTT over WebSocket client we can use
http://www.hivemq.com/demos/websocket-client/
online, or download the Javascript code from
https://github.com/hivemq/hivemq-mqtt-web-client
and run in your browser, with the advantage that you can access your localhost.
I have used ws://broker.mqttdashboard.com with WebSocket on port 8000; no WebSocket over SSL is offered but that should not reduce from the didactic merits of this post.
Every observation for the STOMP over websocket setup can be applied here:
the translation port declaration has the extension "internal"
type port MQTT_IPL4_PT message map to IPL4asp_PT //Translation port
{
out
MQTT_v3_1_1_Message to ASP_Send with f_enc_MQTT_Translation(),
WebSocket_PDU to ASP_Send with f_enc_WS_Translation(),
Composite to ASP_Send with f_enc_HTTP_Translation()
in
MQTT_v3_1_1_Message from ASP_RecvFrom with f_dec_MQTT_Translation(),
HTTP_Message from ASP_RecvFrom with f_dec_HTTP_Translation(),
WebSocket_PDU from ASP_RecvFrom with f_dec_WS_Translation(),
ASP_Event
var integer v_connId
} with {extension "internal"}
so we do not have to generate skeletons.
The translation port and associate function declarations are in MQTT_IPL4_translation.ttcn
External function declarations to extend the IPL4 test port are in:
MQTT_User_CtrlFunct.ttcn
MQTT_User_CtrlFuncDef.cc
The preamble is establishing the TCP/TLS connection and requests the connection upgrade with
template Composite t_http_message (in integer cid, in integer portNr) :={ hTTP_Message:= {
msg := {{request_line :={GET,tsp_url,1,1}},{
host := tsp_hostname&":"&int2str(portNr),
connection := {{"Upgrade"}},
upgrade := {{"websocket"}},
origin := "null",
sec_websocket_key := "dGhlIHNhbXBsZSBub25jZQ==",
sec_websocket_version := "13",
sec_websocket_protocol := "mqttv3.1",
sec_websocket_extensions:= "permessage-deflate"
},omit}},
connId:=cid
}with { optional "implicit omit" }
The postamble is closing the websocket (and optionally tearing down the TCP/TLS connection)
The default altstep
altstep as_default() runs on MQTT_CT system System_CT
{
[] MQTT_PCO.receive(t_publish_r0 ) -> value v_msg {
log("Test publish MQTT response received : ",v_msg);
}
[] MQTT_PCO.receive(MQTT_v3_1_1_Message:?) -> value v_msg {
log("Out of sequence MQTT response received : ",v_msg);
}
[] t.timeout{log("Timeout")}
}
is catching any out-of-sequence message and also timeouts.
the testcase focuses on MQTT:
testcase TC_websocket() runs on MQTT_CT system System_CT {
map(self:MQTT_PCO, system:IPL4_PCO);
f_preamble();
var default v_def := activate(as_default())
//send connect
MQTT_PCO.send(t_connect);
t.start(1.0)
alt
{
[] MQTT_PCO.receive(t_connack) -> value v_msg {
log("MQTT response received : ",v_msg);
}
}
//send subscribe
MQTT_PCO.send(t_subscribe);
//send publish
MQTT_PCO.send(t_publish("Breathe, breathe in the air"));
t.start(10.0)
alt
{
[] MQTT_PCO.receive(t_suback) -> value v_msg {
log("MQTT response received : ",v_msg);
}
}
//send publish
// MQTT_PCO.send(t_publish("Breathe, breathe in the air"));
t.start(10.0)
alt
{
[] MQTT_PCO.receive(t_publish_r) -> value v_msg {
log("MQTT response received : ",v_msg);
}
}
//send unsubscribe
MQTT_PCO.send(t_unsubscribe);
t.start(1.0)
alt
{
[] MQTT_PCO.receive(t_unsuback) -> value v_msg {
log("MQTT response received : ",v_msg);
}
}
//send disconnect
MQTT_PCO.send(t_disconnect);
t.start(1.0)
alt
{
[] MQTT_PCO.receive(MQTT_v3_1_1_Message:?) -> value v_msg {
log("MQTT response received : ",v_msg);
}
}
setverdict(pass);
}
The associated MQTT flow looks as below:
MQTT client (Titan) MQTT broker
+ +
| connect |
+--------------------------->
| connack |
<---------------------------+
| subscribe |
+--------------------------->
| suback |
<---------------------------+
| |
| publish |
+--------------------------->
| publish |
<---------------------------+
| unsubscribe |
+--------------------------->
| unsuback |
<---------------------------+
| |
| |
| disconnect |
+--------------------------->
+ +
The testcase TC_decode() can be used in the following fashion:
-using a client one can connect to an MQTT over WebSocket broker and recored the messaging with Wireshark ( see the capture file attached)
-the extracted WebSocket binary mesages and the contained MQTT payload can then be decoded with TC_decode.
Archive , log files and Wireshark capture attached.
Best regards
Elemer
[Updated on: Sat, 16 September 2017 05:12]
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