Check PORT in Makefile run

Adding this because there's no error message when failed to start the load-balancer because of port in use

Also add HQ_SUBMIT_DELAY_MS for more stable performance

hpc/Makefile

@@ -4,3 +4,15 @@ load-balancer-files = LoadBalancer.cpp LoadBalancer.hpp ../lib/httplib.h ../lib/
 
 build-load-balancer:
 	- g++ -O3 -Wno-unused-result -std=c++17 $(load-balancer-files) -o load-balancer -pthread
+
+run-load-balancer:
+	if ! printenv PORT > /dev/null; then \
+	echo "PORT environment variable not set. Using default value 4242."; \
+	export PORT=4242; \
+	fi && \
+	export HQ_SUBMIT_DELAY_MS=100 && \
+	while nc -z localhost $$PORT; do \
+		read -p "Port $$PORT is already in use. Please enter a different port: " NEW_PORT; \
+		PORT=$${NEW_PORT:-$$PORT}; \
+	done; \
+	./load-balancer