Let's enable support for SSE in all channels as soon as it's ready.

Pref: devtools.netmonitor.features.serverSentEvents

Honza

https://hg.mozilla.org/mozilla-central/rev/ceab66838849

Support for Server Side Events (SSE) should be documented on MDN

Note that we already have MDN page for inspecting WebSockets here:
https://developer.mozilla.org/en-US/docs/Tools/Network_Monitor/Inspecting_web_sockets

There are some test cases that can be used to generated screenshots:

WebSockets

1. Load http://janodvarko.cz/test/websockets/
2. Open DevTools and select the Network panel
3. Click the Connect button on the page
4. Select the new Request entry in the panel
5. Select the Response side panel
6. Click Send button to send (and receive) a WS frame
7. Inspect frames in the side panel

ServerSide Events

1. Load https://farooqar.github.io/sse-echo/
2. Open DevTools and select the Network panel
3. Set the minimum delay (in seconds) between each even to 1
4. Click the Connect button on the page
5. Select the new Request entry in the panel
6. Select the Response side panel
7. Inspect events in the side panel

Both WS and SSE are sharing the same UI - i.e. all messages (events and frames) are displayed in the Response panel as list where the user can:

1. Select individual messages and see the payload at the bottom of the panel
2. Inspect the payload as a raw text or an expandable tree (in case of known format, e.g. JSON)
3. Filter, customize columns, etc. (just like for WS, see https://developer.mozilla.org/en-US/docs/Tools/Network_Monitor/Inspecting_web_sockets)

Supported protocols for SSE:

• Mercure protocol (bug 1645116)
• JSON

New supported protocol for WS:

• STOMP (bug 1606626)
• STOMP inside SockJS (bug 1667751)
  We should update the list in this section:
  https://developer.mozilla.org/en-US/docs/Tools/Network_Monitor/Inspecting_web_sockets#Expanding_each_message

Honza

I've created a page to document SSE in the Netmonitor; see https://developer.mozilla.org/en-US/docs/Tools/Network_Monitor/Inspecting_server-sent_events.

I've also updated the outdated sections of https://wiki.developer.mozilla.org/en-US/docs/Tools/Network_Monitor/Inspecting_web_sockets, and added the new protocol support.

@Chris: this is great, thanks for working on this!

Honza