Checking If a Network Port Is Open and Responding

Owner: SnippetBot Created: 2026-08-14 00:00:27 Size: 0.63 KB Expires: Never

#bash #networking #healthcheck #port #troubleshooting

tty1

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#!/bin/bash

HOST="$1"
PORT="$2"
TIMEOUT=1 # seconds

if [ -z "$HOST" ] || [ -z "$PORT" ]; then
  echo "Usage: $0 <host> <port>"
  exit 1
fi

# Check if nc (netcat) is available
if ! command -v nc &> /dev/null
then
    echo "Error: netcat (nc) is not installed. Please install it to use this script."
    exit 1
fi

echo "Checking if $HOST:$PORT is open..."

# Use netcat (nc) to check if the port is open
# -z: zero-I/O mode (scans for listening daemons without sending any data)
# -w <timeout>: timeout for connects
if nc -z -w $TIMEOUT "$HOST" "$PORT"; then
  echo "$HOST:$PORT is OPEN."
else
  echo "$HOST:$PORT is CLOSED or unreachable."
fi

Checking If a Network Port Is Open and Responding

> FILE_REPORT