Stop a process: kill

$ portcheck kill 3000
About to terminate:
  PID 42379  node  (port 3000)
Proceed? [y/N] y
PID    PROCESS  RESULT      DETAIL
42379  node     terminated

kill finds the processes listening on the given ports (TCP and UDP by default), asks for confirmation, and stops them. The confirmation shows who started each process, which helps you tell your own dev server from something an IDE or another tool is running:

$ portcheck kill 3000
About to terminate:
  PID 42379  node  (port 3000), started by npm (4200) ← zsh (900)
Proceed? [y/N]

How a process is stopped

1. Graceful: portcheck sends SIGTERM, so the program can shut down cleanly.
2. Wait: it waits up to --grace (default 5s) for the process to exit.
3. Force: if the process is still running, it sends SIGKILL.

--force (-f) skips straight to step 3.

Windows

Windows has no general way to ask another process to shut down cleanly, so both steps use TerminateProcess.

The RESULT column says what happened:

Result	Meaning
terminated	exited after the graceful request
killed	had to be force-killed
already-exited	was gone before portcheck could signal it
dry-run	--dry-run: nothing was sent
failed	see DETAIL

Safety

portcheck never kills:

• PID 0 or 1;
• itself, or its parent process (usually your shell).

It also refuses well-known system processes, such as launchd, WindowServer, systemd, init, lsass.exe, csrss.exe and svchost.exe, and container/WSL infrastructure such as com.docker.backend, dockerd, containerd, docker-proxy and wslrelay.exe, unless you pass --allow-system.

Ports published by a container or forwarded from WSL are never handled by killing the proxy: portcheck names the container or distro and suggests docker stop <name> or wsl -d <distro> --exec kill <pid> instead. See Containers & WSL. These checks run before the confirmation prompt, so a refusal never depends on what you answer.

Flags

Flag	Meaning
--pid N	also stop PID N (repeatable); works without a port
--proto tcp	only match ports on this protocol (default tcp,udp)
-y, --yes	don't ask for confirmation
-f, --force	skip the graceful step
--grace 10s	how long to wait before forcing
--dry-run	show what would happen; no confirmation needed
--allow-system	allow protected system processes (dangerous)

Non-interactive use

Without a terminal on stdin (CI, pipes, cron), kill refuses to run unless you pass --yes. This protects you from piping a command into something that kills processes.

portcheck kill 8080 --yes --grace 10s

Exit status

Code	Meaning
0	every target stopped (or dry run)
1	nothing listening, a given PID doesn't exist, you declined, a protected process was refused, or the port belongs to a container
2	invalid arguments, or no --yes without a terminal
3	a process survived SIGKILL, or another error
4	permission denied (the port's owner is hidden, or you can't signal it)

When the result is 4, re-run with sudo or as Administrator; see Permissions by OS.