feat: add port scanner and related makefile

pure-go-port-scanner/Makefile

@@ -0,0 +1,10 @@
+.PHONY: run build clean
+
+run: 
+	go run .
+
+build: clean
+	go build -o bin/scanner scanner.go
+
+clean:
+	rm -rf ./bin/*

pure-go-port-scanner/go.mod

@@ -0,0 +1,3 @@
+module pure_go_port_scanner
+
+go 1.23.1

pure-go-port-scanner/scanner.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net"
+	"sync"
+	"time"
+)
+
+func scanPort(portNumber int) bool {
+	conn, err := net.Dial("tcp", fmt.Sprintf("localhost:%d", portNumber))
+	if err != nil {
+		return false
+	}
+	defer conn.Close()
+	return true
+}
+
+func main() {
+	const MAX_PORT int = 65536
+	wg := sync.WaitGroup{}
+	outCh := make(chan int)
+	totalTime := float64(0)
+
+	log.Println("Starting Port Scan")
+	tx := time.Now()
+
+	for port := 1; port < int(MAX_PORT); port++ {
+		wg.Add(1)
+
+		// dial the port and report the status
+		go func() {
+			tx := time.Now()
+			if scanPort(port) {
+				outCh <- port
+			}
+			td := time.Since(tx)
+			totalTime += td.Seconds()
+			wg.Done()
+		}()
+	}
+
+	// wait for all port scans to complete
+	go func() {
+		wg.Wait()
+		outCh <- -1
+	}()
+
+	// this loop will check both channels and stop when the stopCh receives a signal
+	for p := range outCh {
+		if p == -1 {
+			td := time.Since(tx).Seconds()
+			avg := totalTime / float64(MAX_PORT)
+			log.Printf("!! Scanned %d ports in %f seconds (%f seconds per scan)\n", MAX_PORT, td, avg)
+			return
+		}
+		log.Printf("Open Port: %d", p)
+	}
+}