Refactor Telnet connection handling

Adjusted the Telnet connection process to better handle errors and improve safety. The connection is now established within the New() function and returned with proper error state. This mitigates the risk of working with null or improperly closed connections which existed in the earlier approach.

app/telnet/model.go

@@ -9,6 +9,5 @@ const ctrl = "\r\n"
 type Telnet struct {
 	user string
 	pass string
-	ip   string
-	conn net.Conn
+	Conn net.Conn
 }

app/telnet/telnet.go

@@ -4,25 +4,24 @@ import (
 	"fmt"
 	"net"
 	"strings"
-	"time"
 )
 
-func New(user string, pass string, ip string) *Telnet {
-	return &Telnet{
+func New(user string, pass string, ip string) (*Telnet, error) {
+	conn, err := net.Dial("tcp", ip+":telnet")
+	if err != nil {
+		return nil, err
+	}
+
+	t := &Telnet{
 		user: user,
 		pass: pass,
-		ip:   ip,
+		Conn: conn,
 	}
+
+	return t, nil
 }
 
 func (t *Telnet) PermTelnet() error {
-	conn, err := net.Dial("tcp", t.ip+":telnet")
-	if err != nil {
-		return err
-	}
-	defer conn.Close()
-	t.conn = conn
-
 	if err := t.loginTelnet(); err != nil {
 		return err
 	}
@@ -31,13 +30,6 @@ func (t *Telnet) PermTelnet() error {
 		return err
 	}
 
-	// reboot device
-	fmt.Println("wait reboot..")
-	time.Sleep(time.Second)
-	if err := t.Reboot(); err != nil {
-		return err
-	}
-
 	return nil
 }
 
@@ -60,14 +52,13 @@ func (t *Telnet) modifyDB() error {
 	if err := t.sendCmd(lanEnable, tsLanUser, tsLanPwd, maxConn, initSecLvl, save); err != nil {
 		return err
 	}
-	fmt.Println("Permanent Telnet succeed\r\nuser: root, pass: Zte521")
 
 	return nil
 }
 
 func (t *Telnet) sendCmd(commands ...string) error {
 	cmd := []byte(strings.Join(commands, ctrl) + ctrl)
-	n, err := t.conn.Write(cmd)
+	n, err := t.Conn.Write(cmd)
 	if err != nil {
 		return err
 	}

cmd/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"flag"
 	"fmt"
+	"time"
 
 	"github.com/thank243/zteOnu/app/factory"
 	"github.com/thank243/zteOnu/app/telnet"
@@ -28,9 +29,28 @@ func main() {
 	}
 
 	if *permTelnet {
-		t := telnet.New(tlUser, tlPass, *ip)
+		// create telnet conn
+		t, err := telnet.New(tlUser, tlPass, *ip)
+		if err != nil {
+			fmt.Println(err)
+			return
+		}
+		defer t.Conn.Close()
+
+		// handle permanent telnet
 		if err := t.PermTelnet(); err != nil {
 			fmt.Println(err)
+			return
+		} else {
+			fmt.Println("Permanent Telnet succeed\r\nuser: root, pass: Zte521")
+		}
+
+		// reboot device
+		fmt.Println("wait reboot..")
+		time.Sleep(time.Second)
+		if err := t.Reboot(); err != nil {
+			fmt.Println(err)
+			return
 		}
 	} else {
 		fmt.Printf("user: %s\npass: %s", tlUser, tlPass)