Add transaction IDs to messages and handle on the server

server/asn1/StudySystemProtocol.asn1

@@ -12,12 +12,17 @@ Session ::= SEQUENCE {
 	minutes INTEGER
 }
 
-Request ::= CHOICE {
+RequestBody ::= CHOICE {
 	ping [0] NULL,
 	listPrioritizedActivities [1] NULL,
 	logSession [2] Session
 }
 
+Request ::= SEQUENCE {
+	transactionId INTEGER,
+	body RequestBody
+}
+
 PrioritizedActivity ::= SEQUENCE {
 	subjectId INTEGER,
 	subjectName UTF8String,
@@ -31,10 +36,15 @@ Error ::= ENUMERATED {
 	serverError(2)
 }
 
-Response ::= CHOICE {
+ResponseBody ::= CHOICE {
 	error [0] Error,
 	ack [1] NULL,
 	prioritizedActivities [2] SEQUENCE OF PrioritizedActivity
 }
 
+Response ::= SEQUENCE {
+	transactionId INTEGER,
+	body ResponseBody
+}
+
 END

server/src/session_server.erl

@@ -23,13 +23,16 @@ handle_cast(_Msg, State) ->
 
 handle_info({ssl, Socket, Data}, State) ->
 	case 'StudySystemProtocol':decode('Request', Data) of
-		{ok, {ping, _}} ->
+		{ok, {'Request', TransactionId, RequestBody}} ->
+			ResponseBody = map_request(RequestBody),
 			{ok, Encoded} = 'StudySystemProtocol':encode(
-							  'Response', {ack, 'NULL'}),
+							  'Response',
+							  {'Response', TransactionId, ResponseBody}),
 			ok = ssl:send(Socket, Encoded);
 		{error, {asn1, _Reason}} ->
 			{ok, Encoded} = 'StudySystemProtocol':encode(
-							  'Response', {error, invalidRequest}),
+							  'Response',
+							  {'Response', -1, {error, invalidRequest}}),
 			ok = ssl:send(Socket, Encoded)
 	end,
 	{noreply, State};
@@ -45,3 +48,8 @@ terminate(_Reason, #{socket := Socket}) ->
 
 code_change(_OldVsn, State, _Extra) ->
 	{ok, State}.
+
+map_request({ping, 'NULL'}) ->
+	{ack, 'NULL'};
+map_request(_) ->
+	{error, invalidRequest}.