WebSocket

Stateless roundtrips are fine for click-driven UIs, but some scenarios need the server to push — a news feed, a job-status indicator, a chat. abap2UI5 has no special API for this; you use SAP's standard WebSocket stack and feed the messages into the rendered view via custom JavaScript.

The building blocks:

Layer	Purpose
APC (Application Push Channel, SAPC)	Exposes the WebSocket endpoint over HTTP/S
AMC (Application Messaging Channel, SAMC)	In-system pub/sub — any ABAP code can broadcast into a channel
Custom JS in the view	Opens the socket, dispatches incoming messages

Once both channels are configured, any COMMIT WORK that fires an AMC publish reaches every connected browser within milliseconds — no polling, no timer.

Server Side

An APC class extending cl_apc_wsp_ext_stateless_base binds an AMC consumer when a client connects, so AMC messages are forwarded to that socket. Broadcasting is then a one-liner from anywhere in the system:

DATA(lo_producer) = cl_amc_channel_manager=>create_message_producer(
    i_application_id = `Z2UI5_SAMPLE`
    i_channel_id     = `/news_feed` ).
lo_producer->send( i_message = `New order arrived` ).

A full reference implementation lives in the samples repo — Z2UI5_CL_DEMO_APP_S_05_WS for the APC handler and Z2UI5_CL_DEMO_APP_S_05 for the consuming app.

Client Side

The browser opens the socket via Custom JavaScript embedded in the view. The connection stays open across normal abap2UI5 roundtrips — incoming messages can update a model, trigger a toast, or fire an abap2UI5 event to pull fresh data from the backend:

const ws = new WebSocket("wss://" + window.location.host + "/sap/bc/apc/sap/z2ui5_sample");
ws.onmessage = (e) => {
  sap.m.MessageToast.show(e.data);
};

When to Reach For It

WebSockets cost a permanent connection per user — comparable to a stateful session in resource terms. Use them when push really matters:

• live dashboards, monitoring screens
• multi-user collaboration (chat, shared editing)
• long-running background jobs reporting status

For "refresh every few seconds" the Timer is cheaper and simpler.

WARNING

APC/AMC are not available on every ABAP platform — check release notes for your system (ABAP Cloud, S/4 Public Cloud, BTP ABAP Environment) before designing around them.