Sending request messages to a session
A client session can send a request message containing typed data directly to a client session. The receiving client session can then send a response message containing typed data. The request and response messages are addressed through the same message path.
- A control client session sends a request message to a client session, specifying the message path to send the message through and the session ID of the client session to send the request message to.
- The client session receives the request message through a request stream.
- The client session uses a responder to send a response to the request message.
- The control client session receives the response.
Both the request message and the response message contain typed values. The messages can contain data of one of the following types: JSON, binary, string, 64-bit integer, or double. The response message is not required to be the same data type as the request it responds to.
Sending a request to a session
Required permissions:
permission for the specified message path and permissionUsually, it is a control client session in your organization's backend that sends messages directly to other sessions.
- The session ID of the client session to send the request to
- The message path to send the request and receive the response through
- The request message
- The datatype of the request message
- The datatype of the response message
session.messages.sendRequest('foo', 'Hello client', session_id, diffusion.datatypes.json(), diffusion.datatypes.json())
/** * Copyright © 2021 - 2023 DiffusionData Ltd. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ using System; using System.Threading; using System.Threading.Tasks; using PushTechnology.ClientInterface.Client.Callbacks; using PushTechnology.ClientInterface.Client.Factories; using PushTechnology.ClientInterface.Client.Features; using PushTechnology.ClientInterface.Client.Session; using static System.Console; namespace PushTechnology.ClientInterface.Example { /// <summary> /// Client implementation that sends a request message to a filter, /// then sends another request directly to the session, and displays the response. /// </summary> public sealed class SendingSessionRequestMessages { private readonly string messagingPath = ">random/requestResponse"; public async Task SendingSessionRequestMessagesExample(string serverUrl) { var session = Diffusion.Sessions.Principal( "control" ).Password( "password" ) .CertificateValidation((cert, chain, errors) => CertificateValidationResult.ACCEPT) .Open(serverUrl); var messaging = session.Messaging; var requestCallback = new RequestCallback(); // Filter messaging is used to get the session ID for this example int requestsSent = await messaging.SendRequestToFilterAsync( "$Principal EQ 'client'", messagingPath, "Hello?", requestCallback); Thread.Sleep( 1000 ); // Send message to a session using obtained session ID string response = await messaging.SendRequestAsync<string, string>( requestCallback.SessionId, messagingPath, "Time"); WriteLine($"Received response: '{response}'."); // Close the session session.Close(); } /// <summary> /// A simple IFilteredRequestCallback implementation that prints confirmation of the actions completed. /// </summary> private class RequestCallback : IFilteredRequestCallback<string> { public ISessionId SessionId { get; private set; } /// <summary> /// Indicates that a response message was received. /// </summary> public void OnResponse(ISessionId sessionId, string response) => SessionId = sessionId; /// <summary> /// Indicates that a error response message was received. /// </summary> public void OnResponseError( ISessionId sessionId, Exception exception ) => WriteLine( $"Response error received from session {sessionId}: '{exception}'." ); } } }
//Establish client session and control session final Session control = Diffusion.sessions() .principal("control") .password("password") .open("ws://localhost:8080"); final Session client = Diffusion.sessions() .principal("client") .password("password") .open("ws://localhost:8080"); //Obtain the Messaging and MessagingControl features final Messaging messagingControl = control.feature(Messaging.class); final Messaging messaging = client.feature(Messaging.class); //Create a JSON object to send as a request final JSON request = Diffusion.dataTypes().json().fromJsonString("\"hello\""); //Create a local request stream for the client to receive direct requests from the control session messaging.setRequestStream("foo", JSON.class, JSON.class, new JSONRequestStream()); //Send the request to a message path "foo" and wait for (at most) 5 seconds until the response is received. final JSON response = messagingControl.sendRequest( client.getSessionId(), "foo", request, JSON.class, JSON.class).get(5, TimeUnit.SECONDS);
BUF_T *message_buf = buf_create(); write_diffusion_string_value(message, message_buf); SEND_REQUEST_TO_SESSION_PARAMS_T params = { .recipient_session = session_id, .path = message_path, .request = message_buf, .request_datatype = DATATYPE_STRING, .response_datatype = DATATYPE_STRING, .on_response = on_message_response }; send_request_to_session(session, params); buf_free(message_buf);
# Sending the request and receiving the response. print(f"Sending request: '{request}' to session {session_id}...") try: response = await session.messaging.send_request_to_session( path=path, session_id=session_id, request=request_type(request) ) except diffusion.DiffusionError as ex: print(f"ERROR: {ex}") else: print(f"... received response '{response}'")
let json_request = try! PTDiffusionJSON(jsonString: "{\"hello\": \"world\"}").request session.messaging.send(json_request, to: session_id, path: message_path, jsonCompletionHandler: { (response: PTDiffusionJSON?, error) in if (error != nil) { print("Failed to send message to %@. Error: %@", message_path, error!.localizedDescription) } else { print("Received response: %@", response!) } })
Responding to messages sent to a session
Required permissions:
for the specified message pathDefine a request stream to receive and respond to request messages that have a specific data type.
const handler = { onRequest : function(request, context, responder) { /// ... responder.respond(response); }, onError : (error) => { // an error occured }, onClose : () => { // the handler is closed } }
/** * Copyright © 2021 - 2023 DiffusionData Ltd. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ using System; using System.Threading; using PushTechnology.ClientInterface.Client.Callbacks; using PushTechnology.ClientInterface.Client.Factories; using PushTechnology.ClientInterface.Client.Features; using static System.Console; namespace PushTechnology.ClientInterface.Example { /// <summary> /// A simple IRequestStream implementation that prints confirmation of the actions completed. /// </summary> internal class SimpleSessionMessagesRequestStream : IRequestStream<string, string> { /// <summary> /// Indicates that the request stream was closed. /// </summary> public void OnClose() => WriteLine( "A request handler was closed." ); /// <summary> /// Indicates that the request stream has received error. /// </summary> public void OnError( ErrorReason errorReason ) => WriteLine( $"A request handler has received error: {errorReason}." ); /// <summary> /// Indicates that a request was received and responds to it. /// </summary> /// <remarks>On invalid request you would call: <see cref="IResponder{TResponse}.Reject(string)"/>.</remarks> public void OnRequest( string path, string request, IResponder<string> responder ) { if ( request == "Hello?" ) { // message to the filter to obtain the session ID responder.Respond( "Yes" ); } else { WriteLine( $"Received request: '{request}'." ); responder.Respond( DateTime.UtcNow.ToLongTimeString() ); } } } }
private static class JSONRequestStream implements Messaging.RequestStream<JSON, JSON> { @Override public void onRequest(String path, JSON request, Responder<JSON> responder) { final JSON response = Diffusion.dataTypes().json().fromJsonString("\"world\""); responder.respond(response); } @Override public void onClose() { } @Override public void onError(ErrorReason errorReason) { } }
/** * Copyright © 2021 - 2023 DiffusionData Ltd. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. * */ #include <stdio.h> #include <stdlib.h> #ifndef WIN32 #include <unistd.h> #else #define sleep(x) Sleep(1000 * x) #endif #include "diffusion.h" static int on_selected_sessions_received( int number_sent, void *context) { // `number_sent` is the number of sessions selected by the `session_filter` return HANDLER_SUCCESS; } static int on_message_response( DIFFUSION_DATATYPE response_datatype, const DIFFUSION_VALUE_T *response, void *context) { // read the `response` by converting it to the datatype `response_datatype` return HANDLER_SUCCESS; } void to_filter( SESSION_T *session, char *message_path, char *message, char *session_filter) { BUF_T *message_buf = buf_create(); write_diffusion_string_value(message, message_buf); SEND_REQUEST_TO_FILTER_PARAMS_T params = { .path = message_path, .filter = session_filter, .request_datatype = DATATYPE_STRING, .response_datatype = DATATYPE_STRING, .request = message_buf, .on_response = on_message_response, .on_number_sent = on_selected_sessions_received }; send_request_to_filter(session, params); buf_free(message_buf); } void to_session( SESSION_T *session, char *message_path, char *message, SESSION_ID_T *session_id) { BUF_T *message_buf = buf_create(); write_diffusion_string_value(message, message_buf); SEND_REQUEST_TO_SESSION_PARAMS_T params = { .recipient_session = session_id, .path = message_path, .request = message_buf, .request_datatype = DATATYPE_STRING, .response_datatype = DATATYPE_STRING, .on_response = on_message_response }; send_request_to_session(session, params); buf_free(message_buf); } static int on_message_request( SESSION_T *session, const char *request_path, DIFFUSION_DATATYPE request_datatype, const DIFFUSION_VALUE_T *request, const DIFFUSION_RESPONDER_HANDLE_T *handle, void *context) { // read the `request` based on the received `request_datatype` char *request_val; read_diffusion_string_value(request, &request_val, NULL); printf("Received message: %s\n", request_val); free(request_val); // create the response BUF_T *response_buf = buf_create(); write_diffusion_string_value("This is my response", response_buf); // and respond to the request diffusion_respond_to_request(session, handle, response_buf, NULL); buf_free(response_buf); return HANDLER_SUCCESS; } void register_request_stream( SESSION_T *session, char *message_path) { DIFFUSION_REQUEST_STREAM_T request_stream = { .on_request = on_message_request }; set_request_stream(session, message_path, DATATYPE_STRING, DATATYPE_STRING, &request_stream); } void to_path( SESSION_T *session, char *message_path, char *message) { BUF_T *message_buf = buf_create(); write_diffusion_string_value(message, message_buf); SEND_REQUEST_PARAMS_T params = { .path = message_path, .request = message_buf, .on_response = on_message_response, .request_datatype = DATATYPE_STRING, .response_datatype = DATATYPE_STRING }; send_request(session, params); buf_free(message_buf); } static int on_request_handler_active( SESSION_T *session, const char *path, const DIFFUSION_REGISTRATION_T *registered_handler) { // message path `path` is now active for `registered_handler` return HANDLER_SUCCESS; } static int on_request_received( SESSION_T *session, DIFFUSION_DATATYPE request_datatype, const DIFFUSION_VALUE_T *request, const DIFFUSION_REQUEST_CONTEXT_T *request_context, const DIFFUSION_RESPONDER_HANDLE_T *handle, void *context) { // handle request received // and response to request with // `diffusion_respond_to_request(session, handle, response, NULL)` return HANDLER_SUCCESS; } void register_request_handler( SESSION_T *session, char *message_path) { DIFFUSION_REQUEST_HANDLER_T request_handler = { .request_datatype = DATATYPE_STRING, .response_datatype = DATATYPE_STRING, .on_active = on_request_handler_active, .on_request = on_request_received }; ADD_REQUEST_HANDLER_PARAMS_T params = { .path = message_path, .request_handler = &request_handler }; add_request_handler(session, params); } int main(int argc, char **argv) { const char *url = "ws://localhost:8080"; const char *principal = "control"; const char *password = "password"; CREDENTIALS_T *credentials = credentials_create_password(password); SESSION_T *session = session_create(url, principal, credentials, NULL, NULL, NULL); SESSION_ID_T *session_id = session_id_create_from_string("e9cfbd5be9a72622-f000000300000004"); char *message_path = "message/path"; char *message = "hello world"; char *session_filter = "$Principal is 'control'"; to_filter(session, message_path, message, session_filter); to_session(session, message_path, message, session_id); to_path(session, message_path, message); register_request_handler(session, message_path); // Sleep for a while sleep(5); // Close the session, and release resources and memory session_close(session, NULL); session_free(session); credentials_free(credentials); session_id_free(session_id); return EXIT_SUCCESS; }
def callback(request: str, **kwargs) -> str: return diffusion.datatypes.STRING(f"Hello there, {request}!")
class JSONRequestStreamDelegate: PTDiffusionJSONRequestStreamDelegate { func diffusionStream(_ stream: PTDiffusionStream, didReceiveRequestWith json: PTDiffusionJSON, responder: PTDiffusionResponder) { print("Received request %@", json) let json_response = try! PTDiffusionJSON(jsonString: "{\"greetings\": \"stranger\"}").response responder.respond(with: json_response) } func diffusionStream(_ stream: PTDiffusionStream, didFailWithError error: Error) { print("Request stream failed with error %@", error.localizedDescription) } func diffusionDidClose(_ stream: PTDiffusionStream) { print("Request stream is now closed") } }
Add the request stream against a message path. You can only add one request stream for each message path.
session.messages.setRequestStream("foo", handler, diffusion.datatypes.json(), diffusion.datatypes.json(), );
/** * Copyright © 2021 - 2023 DiffusionData Ltd. * * Licensed under the Apache License, Version 2.0 (the "License"); * you may not use this file except in compliance with the License. * You may obtain a copy of the License at * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ using System; using System.Threading; using PushTechnology.ClientInterface.Client.Factories; namespace PushTechnology.ClientInterface.Example { /// <summary> /// Client implementation that registers a handler to listen for messages on a path. /// </summary> public sealed class ReceivingSessionRequestMessages { public void ReceivingSessionRequestMessagesExample(string serverUrl) { var session = Diffusion.Sessions.Principal( "client" ).Password( "password" ).Open( serverUrl ); var messaging = session.Messaging; string messagingPath = ">random/requestResponse"; var requestStream = new SimpleSessionMessagesRequestStream(); messaging.SetRequestStream( messagingPath, requestStream ); try { Thread.Sleep( 60000 ); // wait for messages... } finally { // Close session messaging.RemoveRequestStream( messagingPath ); session.Close(); } } } }
messaging.setRequestStream("foo", JSON.class, JSON.class, new JSONRequestStream());
static int on_message_request( SESSION_T *session, const char *request_path, DIFFUSION_DATATYPE request_datatype, const DIFFUSION_VALUE_T *request, const DIFFUSION_RESPONDER_HANDLE_T *handle, void *context) { // read the `request` based on the received `request_datatype` char *request_val; read_diffusion_string_value(request, &request_val, NULL); printf("Received message: %s\n", request_val); free(request_val); // create the response BUF_T *response_buf = buf_create(); write_diffusion_string_value("This is my response", response_buf); // and respond to the request diffusion_respond_to_request(session, handle, response_buf, NULL); buf_free(response_buf); return HANDLER_SUCCESS; } void register_request_stream( SESSION_T *session, char *message_path) { DIFFUSION_REQUEST_STREAM_T request_stream = { .on_request = on_message_request }; set_request_stream(session, message_path, DATATYPE_STRING, DATATYPE_STRING, &request_stream); }
# Register handler to receive the request handler = RequestHandler( callback, request_type=request_type, response_type=request_type ) session.messaging.add_stream_handler(path, handler=handler, addressed=True)
let stream_delegate = JSONRequestStreamDelegate() let request_stream = PTDiffusionJSON.requestStream(with: stream_delegate) session.messaging.setRequestStream(request_stream, forPath: message_path)