Complete the WebSocket opening handshake before processing data frames

Use this document to connect an official requirement or behavior to observable evidence: Complete the WebSocket opening handshake before processing data frames. Only the official source and traced locations below supply facts. Confirm applicability before acting.

Source fact:

The official RFC 6455 — The WebSocket Protocol from RFC Editor / Internet Engineering Task Force supports the following bounded statements:

• A server rejects a WebSocket opening request that lacks the required GET, Host, Upgrade, Connection, 16-byte encoded key, or version-13 fields. The research record locates this support at Section 4.2.1 (Reading the Client’s Opening Handshake).
• Accepting the connection requires status 101, Upgrade and Connection fields, and Sec-WebSocket-Accept computed from the client’s key and the protocol GUID. The research record locates this support at Section 4.2.2 (Sending the Server’s Opening Handshake), step 5.
• Either endpoint may send data frames only after the opening handshake completes and before that endpoint sends a Close frame; client frames are masked and server frames are not. The research record locates this support at Section 5.1 (Overview).

These statements are the factual basis for this document. Do not extend them into a broader assurance. Review clients, origin services, intermediaries, caches, proxies, gateways, protocol versions, and security-policy enforcement points only where the source and recorded environment align.

What the source does not establish

This RFC evidence supports only the named web or transport decision; it does not prove browser, intermediary, library, or service compatibility. It does not establish a deployment’s current state, authorize a production change, prove compliance, or show that DNS, certificates, identity providers, time, content delivery, network paths, and application ownership are healthy. Documented options are review inputs, not universal mandates.

Applicability questions

• For source statement 1 at Section 4.2.1 (Reading the Client’s Opening Handshake), which observable configuration, record, or test can confirm applicability here?
• For source statement 2 at Section 4.2.2 (Sending the Server’s Opening Handshake), step 5, which observable configuration, record, or test can confirm applicability here?
• For source statement 3 at Section 5.1 (Overview), which observable configuration, record, or test can confirm applicability here?
• What inventory proves which parts of clients, origin services, intermediaries, caches, proxies, gateways, protocol versions, and security-policy enforcement points are in and out of scope?
• Which condition in DNS, certificates, identity providers, time, content delivery, network paths, and application ownership must be healthy before evidence is trustworthy?
• What result would disprove the working assumption and return the issue to the owner?

DSE recommendation:

DSE recommends using the cited source as the evidence anchor for this decision. Start with applicability, then compare the observed state with the cited source. Record the source location, examined part of clients, origin services, intermediaries, caches, proxies, gateways, protocol versions, and security-policy enforcement points, observed and expected states, owner, and reason for deviation.

An implementation decision needs an owner, approved window, prechecks, observable outcome, stop authority, and rollback path. Validate DNS, certificates, identity providers, time, content delivery, network paths, and application ownership before and after the test, and store only sanitized operational evidence.

Verification and evidence

Build a reproducible chain from Section 4.2.1 (Reading the Client’s Opening Handshake); Section 4.2.2 (Sending the Server’s Opening Handshake), step 5; Section 5.1 (Overview) to the observed environment. Useful domain evidence includes request and response captures, negotiated protocol details, headers, cache behavior, certificate state, and server or proxy logs; label every item with scope, timestamp, collector, and stable identifier.

Record the decision even when no change is made, including uncertainty and the next trigger. Use safe testing conditions for disruptive work, preserve rollback proof, and revisit the conclusion after relevant platform, dependency, vendor, or ownership changes.

Official references

• RFC 6455 — The WebSocket Protocol — RFC Editor / Internet Engineering Task Force