killport — kill whatever is listening on a TCP port (LISTEN sockets only, so clients connected to the port are left alone)

killport

#!/usr/bin/env bash
# killport <port> [signal]
# Kill whatever is *listening* on a TCP port (not clients merely connected to it).
set -euo pipefail

port="${1:-}"
signal="${2:-TERM}"

if [[ -z "$port" || ! "$port" =~ ^[0-9]+$ ]]; then
  echo "usage: killport <port> [signal]" >&2
  exit 1
fi

# Only listening sockets — avoids killing clients with an established connection.
pids="$(lsof -tiTCP:"$port" -sTCP:LISTEN 2>/dev/null || true)"

if [[ -z "$pids" ]]; then
  echo "Nothing listening on port $port"
  exit 0
fi

for pid in $pids; do
  cmd="$(ps -p "$pid" -o comm= 2>/dev/null || echo '?')"
  echo "Killing $pid ($cmd) on port $port with SIG$signal"
  kill -"$signal" "$pid" 2>/dev/null || true
done