Merge pull request #749 from devlights/add-simple-port-scanner

Author: devlights

examples/singleapp/simple_port_scan/Taskfile.yml

@@ -0,0 +1,8 @@
+# https://taskfile.dev
+
+version: '3'
+
+tasks:
+  run:
+    cmds:
+      - go run main.go -debug 127.0.0.1 50010 50020

examples/singleapp/simple_port_scan/main.go

@@ -0,0 +1,83 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"log"
+	"net"
+	"os"
+	"strconv"
+	"time"
+)
+
+type Args struct {
+	host string
+	from int
+	to   int
+}
+
+var (
+	debug = flag.Bool("debug", false, "debug")
+	args  = Args{}
+)
+
+func init() {
+	log.SetFlags(0)
+}
+
+func panicErr[T any](o T, err error) T {
+	if err != nil {
+		log.Panic(err)
+	}
+
+	return o
+}
+
+func main() {
+	flag.Parse()
+
+	if flag.NArg() != 3 {
+		log.Println("Usage: simple_port_scan host port(from) port(to)")
+		os.Exit(1)
+	}
+
+	a := flag.Args()
+	args.host = a[0]
+	args.from = panicErr(strconv.Atoi(a[1]))
+	args.to = panicErr(strconv.Atoi(a[2]))
+
+	var l net.Listener
+	var e error
+	if *debug {
+		l, e = net.Listen("tcp4", fmt.Sprintf("127.0.0.1:%d", ((args.to-args.from)/2)+args.from))
+		if e != nil {
+			log.Println(e)
+		}
+	}
+	defer l.Close()
+
+	if err := run(); err != nil {
+		log.Panic(err)
+	}
+}
+
+func run() error {
+	for i := args.from; i <= args.to; i++ {
+		var (
+			addr = fmt.Sprintf("%s:%d", args.host, i)
+			conn net.Conn
+			err  error
+		)
+
+		conn, err = net.DialTimeout("tcp4", addr, 1*time.Second)
+		switch err {
+		case nil:
+			log.Printf("%d open", i)
+			conn.Close()
+		default:
+			log.Printf("%d closed", i)
+		}
+	}
+
+	return nil
+}