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v2/server/rack: negotiate the WebSocket subprotocol (RFC 6455) #27

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Merged
bradgessler merged 1 commit into from
Jun 22, 2026
Merged

v2/server/rack: negotiate the WebSocket subprotocol (RFC 6455) #27

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20 changes: 18 additions & 2 deletions v2/ruby/lib/terminalwire/v2/server/rack.rb
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Original file line number Diff line number Diff line change
Expand Up @@ -37,6 +37,12 @@ module Server
class Rack
WS_GUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11"

# WebSocket subprotocols this server speaks, best first. The handshake echoes
# the first one the client also offered (RFC 6455 negotiation) — the v1 handler
# did this (`protocols: ['ws']`) and some edges/proxies (e.g. Fly) drop a
# WebSocket whose Sec-WebSocket-Protocol the server never echoes back.
SUBPROTOCOLS = %w[terminalwire.v2 ws].freeze

# @param cli_class [Class] a Thor CLI that includes Terminalwire::V2::Server::Thor
# @param verbose [Boolean] send full backtraces to the client (dev only)
# @param report [#call, nil] optional callable invoked with unexpected errors
Expand All @@ -56,7 +62,7 @@ def call(env)
# adapter in here — this is the only path that needs the async stack.
# :nocov: Falcon transport wiring — exercised live by the conformance suite, not units.
require "async/websocket/adapters/rack"
Async::WebSocket::Adapters::Rack.open(env) { |connection| ReactorBridge.new(connection, @handler, request: request).run }
Async::WebSocket::Adapters::Rack.open(env, protocols: SUBPROTOCOLS) { |connection| ReactorBridge.new(connection, @handler, request: request).run }
# :nocov:
else
# Threaded server (Puma & friends): hand-roll the upgrade and stream.
Expand Down Expand Up @@ -119,7 +125,17 @@ def websocket?(env)

def upgrade_headers(env)
accept = [Digest::SHA1.digest("#{env['HTTP_SEC_WEBSOCKET_KEY']}#{WS_GUID}")].pack("m0")
{ "upgrade" => "websocket", "connection" => "Upgrade", "sec-websocket-accept" => accept }
headers = { "upgrade" => "websocket", "connection" => "Upgrade", "sec-websocket-accept" => accept }
if (proto = negotiated_subprotocol(env))
headers["sec-websocket-protocol"] = proto
end
headers
end

# The first subprotocol both we and the client support (RFC 6455), or nil.
def negotiated_subprotocol(env)
offered = env["HTTP_SEC_WEBSOCKET_PROTOCOL"].to_s.split(/,\s*/)
(SUBPROTOCOLS & offered).first
end

def upgrade_required
Expand Down
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