First quick & dirty Go code

knockr.go

@@ -0,0 +1,60 @@
+package main
+
+import (
+	"fmt"
+	"io"
+	"net"
+)
+
+var whitelist []string
+
+func main() {
+	ln, err := net.Listen("tcp", ":8080")
+
+	if err != nil {
+		fmt.Println("Errur on Listening")
+	} else {
+		for {
+			conn, err := ln.Accept()
+			if err != nil {
+				fmt.Println("Errur on Accepting")
+			} else {
+				go handle(conn)
+			}
+		}
+	}
+}
+
+func handle(c net.Conn) {
+	host, _, _ := net.SplitHostPort(c.RemoteAddr().String())
+
+	io.WriteString(c, "Knock Knock, ")
+	io.WriteString(c, host)
+	io.WriteString(c, ". ")
+
+	if is_whitelisted(host) {
+		io.WriteString(c, "You're whitelisted.")
+	} else {
+		io.WriteString(c, "You're not whitelisted.")
+	}
+
+	add_to_whitelist(host)
+
+	c.Close()
+}
+
+func add_to_whitelist(addr string) {
+	if ! is_whitelisted(addr) {
+		whitelist = append(whitelist, addr)
+	}
+}
+
+func is_whitelisted(addr string) bool {
+	for i:=0; i < len(whitelist); i++ {
+		if whitelist[i] == addr {
+			return true
+		}
+	}
+
+	return false
+}