Datagram

[EducatedSuddenBucket]

Datagram/UDP when

[brianathere]

I would like to add a concrete request for outbound UDP client support in Workers, scoped narrowly enough to be useful for QUIC/HTTP/3 clients without requiring a full general-purpose UDP server surface.

Current state, as I understand it:

• cloudflare:sockets gives Workers a TCP client surface, but I do not see an equivalent datagram/UDP client API.
• The Workers Node.js compatibility docs list node:dgram as a non-functional stub enabled with nodejs_compat on or after 2026-01-29.
• The workerd implementation appears intentionally import-compatible rather than transport-capable; it lets packages load, but it is not suitable for application UDP traffic.

The minimum useful API for client-side QUIC/HTTP/3 would be much smaller than full Node dgram support:

• outbound-only UDP client sockets
• connect/send/receive/close
• destination host/port
• error/close signaling
• datagram payloads of at least QUIC's 1200-byte minimum initial packet size, preferably enough for ordinary path MTU-sized packets
• no multicast, broadcast, UDP server listen socket, or arbitrary privileged binding needed for this use case

Either of these shapes would unblock real client work:

• a Workers-native cloudflare:sockets datagram API, for example connectDatagram({ hostname, port }) with readable/writable datagram streams, or
• a functional outbound-client subset of node:dgram, such as createSocket("udp4").connect(port, host), send(), message events, close, and error events.

This would unlock Workers-hosted clients for protocols that are currently unreachable from Workers despite fitting the rest of the isolate model well: HTTP/3/QUIC, DNS transports that are not using fetch/DoH, syslog/metrics sinks, game/server status protocols such as Minecraft Bedrock, and other UDP-based client protocols.

For my immediate case, I am working on an HTTP/3 client library that can be structured as a sans-IO QUIC/HTTP/3 core plus a small host datagram adapter. Workers already have enough WebAssembly/JS capability for the protocol logic; the missing primitive is just outbound datagram I/O.