feat: add script to check if a port is publicly accesible

Performs a request to https://canyouseeme.org and checks its output for success

check-port-open/check-port-open.sh

@@ -0,0 +1,31 @@
+#!/usr/bin/bash
+
+MIN_PORT=1
+MAX_PORT=65535
+
+PORT=$1
+
+if [ ! $PORT ]; then
+  echo "Usage: $0 <PORT>"
+  exit 10
+fi
+
+if [ $PORT -lt $MIN_PORT ] || [ $PORT -gt $MAX_PORT ]; then
+  echo "Port must be a number between $MIN_PORT and $MAX_PORT"
+  exit 11
+fi
+
+echo "Checking wether port $PORT is open"
+
+RESPONSE=$(curl -s -X POST --url https://canyouseeme.org -d port=$PORT)
+
+echo $RESPONSE | grep -i "I can see your service on" > /dev/null
+SUCCESS=$?
+
+if [ $SUCCESS -eq 0 ]; then
+  echo "Port $PORT is open"
+  exit 0
+else
+  echo "Port $PORT is not open"
+  exit 1
+fi