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RFC 8441 / WEBSOCKETS ON HTTP/2

Replace the opening handshake

02

Extended CONNECT names the WebSocket service and target URI; a successful response opens this stream for WebSocket traffic.

DIAGRAMRead RFC section 4 ↗
RFC 8441 · § 4EXAMPLE
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Replace the opening handshakeDecoded HEADERS example for wss://server.example.com/chat uses methodCONNECT, protocolwebsocket, schemehttps, path/chat and authorityserver.example.com. Remaining WebSocket negotiation uses lowercase fields. The server example returns status200 and selected chat; neither101 nor old key/accept processing is used. Open state follows successful handshake processing.Open WebSocket on the CONNECT streamwss://server.example.com/chatDecoded HEADERS fields · not HTTP/1 wire text:method = CONNECT:protocol = websocket:scheme = https:path = /chat:authority = server.example.comsec-websocket-version = 13sec-websocket-protocol = chat, superchatorigin = https://app.example:status = 200sec-websocket-protocol = chatSuccessful handshake → WebSocket OPEN
03
Accept the handshake on this stream.

The server’s illustrative 200 response selects chat from the offered subprotocols. No 101 or old key/accept challenge is used. Only after success does this stream carry WebSocket traffic.

Source for this drawing: RFC 8441 · Read RFC section 4 ↗

Protocol participantThreat or exceptionProtocol controlSimplified drawings · precise section references
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A message needs an address.

Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.

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RFC 6455 WebSocket RFC 9113 HTTP/2 RFC 9110 HTTP

These pictures are analogies to help you learn. The linked RFC explains the actual rules.

Terms in this drawing
Extended CONNECT
The opted-in CONNECT form with a :protocol pseudo-header.
Subprotocol
An application protocol negotiated inside WebSocket, such as the illustrative chat value.
HEADERS
HTTP/2 frames carrying compressed field sections; the drawing shows decoded fields.
Related RFCs and changes

“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.

KEY POINT

Change the handshake, not the whole connection.

  • The request MUST include :protocol with value websocket. Requests bearing :protocol MUST also include :scheme and :path. :authority identifies the target resource, not an instruction to tunnel to that external host.
  • For wss, :scheme MUST be https; for ws it MUST be http. Connection and Upgrade MUST NOT be included. Implementations do not perform the old Sec-WebSocket-Key / Sec-WebSocket-Accept processing.
  • Origin, Sec-WebSocket-Version, subprotocol and extension fields retain their RFC6455 roles; HTTP/2 field names are lowercase. After a successful opening handshake the WebSocket state is OPEN. The example uses status 200, not 101.
DETAILS

The server MUST NOT create the ordinary CONNECT tunnel to the host in :authority merely because Extended CONNECT uses that name; the selected protocol service can be co-located or elsewhere. The displayed list is a decoded HEADERS field example, not literal HTTP/1 text on the wire. No extension is offered here.

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