Relay · Agent

The relay for every port you can't expose.

HTTP, WebSocket, raw TCP — one lightweight agent connects your machine to the internet. Spin up a public URL in seconds, watch traffic land, route by serverId.

Open Agent →Start as guest

LIVE

Mercur / relay · sid_7a3f

HTTP · webhooksWebSocket · streamsRaw TCP · databases14,832 req / 24h · avg 127ms

Features

Everything you need to expose localhost.

Every card below maps to something you can do in the product today. Nothing hidden behind a sales call.

Route by serverId

One agent, many subdomains. Each proxy server gets its own URL, config, and isolated log stream.

HTTP · WS · TCP

Webhooks, realtime streams, raw sockets — all three shapes of traffic managed from one place.

Runtime toggle

Start and stop servers without restarting the agent. Take a session offline mid-debug, resume instantly.

Incoming request log

Full headers, bodies, timing. Replay any request against your local target. Nothing leaves your box unless it has to.

Agent API tokens

Scope tokens per machine, rotate on demand. Revoke a laptop without touching the rest of your stack.

Access rules

IP whitelists, CIDR blocks, bearer guards. Start open, close down as trust builds.

How it works

Account, route, agent, traffic.

Four steps. None require reading the manual first.

Account or guest

Configure a server

Pick protocol, point at localhost. You get back a subdomain for HTTP/WS and a numbered port for TCP.

Connect the agent

Connect the local agent from the app. It opens a tunnel to the relay and waits for traffic.

Observe traffic

Every request appears with timing, headers, body. Replay failed ones against your local target.

Use cases

Three shapes of traffic.

One agent handles every protocol. Start with one route; run several at once when it grows.

HTTP · webhooks

Stripe, Linear, GitHub

A public URL that forwards to your local dev server. Replay any webhook against a new handler without waiting for the upstream to retry.

Agent · HTTP · localhost:3000

WebSocket · streams

Realtime & pub/sub

Expose a local socket server to a staging client. Keep a session open for hours; the relay holds the connection when your wifi drops.

Agent · WebSocket · localhost:8080

Raw TCP · sockets

Postgres, Redis, SSH

Give a teammate one-port access to a local database. Revoke the token when the ticket closes.

Agent · TCP · localhost:5432

Start

A relay endpoint, in the next 30 seconds.

Guest mode gets you a working URL before the coffee cools.

Start as guest Open Agent