You can use the CLI to forward one or more local ports to a pod. This allows you to listen on a given or random port locally, and have data forwarded to and from given ports in the pod.
Support for port forwarding is built into the CLI:
$ oc port-forward <pod> [<local_port>:]<remote_port> [...[<local_port_n>:]<remote_port_n>]
The CLI listens on each local port specified by the user, forwarding via the protocol described below.
Ports may be specified using the following formats:
5000
|
The client listens on port 5000 locally and forwards to 5000 in the pod. |
6000:5000
|
The client listens on port 6000 locally and forwards to 5000 in the pod. |
:5000 or 0:5000
|
The client selects a free local port and forwards to 5000 in the pod. |
{product-title} handles port-forward requests from clients. Upon receiving a request, {product-title} upgrades the response and waits for the client to create port-forwarding streams. When {product-title} receives a new stream, it copies data between the stream and the pod’s port.
Architecturally, there are options for forwarding to a pod’s port. The supported {product-title} implementation invokes nsenter directly on the node host
to enter the pod’s network namespace, then invokes socat to copy data between the stream and the pod’s port. However, a custom implementation could
include running a helper pod that then runs nsenter and socat, so that those binaries are not required to be installed on the host.