Exposed ports
Expose a port when you want to open a server that runs inside the cloud environment – a dev server, an API, or a preview build – from your browser.
The agent often starts a server in the cloud environment: a dev server, a preview build, or an API the tests call. Such a server listens inside the container, so a localhost address means nothing on your machine. Instead, JetBrains Air Teams publishes each exposed port at its own public URL. Only HTTP is supported.
Use Exposed ports to list the ports the environment publishes. Enter them as a comma-separated list, for example 3000, 5173. Each port must be in the range 1–65535.
By default, the environment exposes ports 3000, 8000, and 8080, which cover most dev servers. Change the list when your project serves on a different port, for example, 5173 for a Vite dev server or 4200 for Angular.
List only the ports you need. An environment has a fixed bandwidth budget for exposed-port traffic and the ports share it equally, so each extra port leaves the others with less.
Make the server reachable
Exposing the port is not enough on its own. The server also has to accept a request that arrives from outside the container:
Listen on
0.0.0.0– a server bound to127.0.0.1accepts connections only from inside the container, so the public URL returns nothing.Accept the public hostname – the request reaches the server with the public hostname in the
Hostheader, and a framework that checks that header rejects a host it doesn't know. Allow the host in the framework's own setting, for example,server.allowedHostsin Vite orallowedHostsin the Angular dev server.
Absolute URLs the server generates itself – hot-reload sockets, redirects, asset links – have to point at the public origin too, not at localhost.
Find the public URL of a port
Inside the environment, each exposed port gets an environment variable named JBCENTRAL_EXPOSED_PORT_URL_<port> that holds the full URL. Ask the agent to print the one you need:
JetBrains Air Teams sets these variables when the environment starts, and a resumed task gets the same values, so the URL stays valid for the whole task. The agent session and .air/cloud/startup.sh both read them, so the script can point a config file or a framework setting at the public URL before the server starts.