simple telnetd

main.go

// This was coded by claude.ai

package main

import (
    "bufio"
    "fmt"
    "net"
    "os"
    "os/exec"
    "strings"
)

var serverPassword string

func main() {
    // Get port number from console
    fmt.Print("Enter port number (default 2323): ")
    portScanner := bufio.NewScanner(os.Stdin)
    portScanner.Scan()
    port := strings.TrimSpace(portScanner.Text())
    if port == "" {
        port = "2323"
    }
    
    // Get password from console at startup
    fmt.Print("Set server password (empty for no auth): ")
    passwordScanner := bufio.NewScanner(os.Stdin)
    passwordScanner.Scan()
    serverPassword = strings.TrimSpace(passwordScanner.Text())
    fmt.Println() // New line after password input

    listener, err := net.Listen("tcp", ":"+port)
    if err != nil {
        fmt.Printf("Error starting server: %v\n", err)
        return
    }
    defer listener.Close()

    if serverPassword == "" {
        fmt.Printf("Telnet server listening on :%s (NO AUTHENTICATION)\n", port)
    } else {
        fmt.Printf("Telnet server listening on :%s (Password required)\n", port)
    }

    for {
        conn, err := listener.Accept()
        if err != nil {
            fmt.Printf("Error accepting connection: %v\n", err)
            continue
        }
        
        go handleConnection(conn)
    }
}

func handleConnection(conn net.Conn) {
    defer conn.Close()
    
    conn.Write([]byte("Welcome to Telnet Server\r\n"))
    
    // Authentication if password is set
    if serverPassword != "" {
        conn.Write([]byte("Password: "))
        
        scanner := bufio.NewScanner(conn)
        if !scanner.Scan() {
            return
        }
        
        inputPassword := strings.TrimSpace(scanner.Text())
        if inputPassword != serverPassword {
            conn.Write([]byte("Access denied\r\n"))
            return
        }
        conn.Write([]byte("Authentication successful\r\n"))
    }
    
    conn.Write([]byte("Type 'exit' to quit\r\n\r\n"))
    conn.Write([]byte("$ "))

    scanner := bufio.NewScanner(conn)
    
    for scanner.Scan() {
        command := strings.TrimSpace(scanner.Text())
        
        if command == "exit" || command == "quit" {
            conn.Write([]byte("Goodbye!\r\n"))
            break
        }
        
        if command == "" {
            conn.Write([]byte("$ "))
            continue
        }
        
        // Execute command
        cmd := exec.Command("sh", "-c", command)
        output, err := cmd.CombinedOutput()
        
        if err != nil {
            conn.Write([]byte(fmt.Sprintf("Error: %v\r\n", err)))
        } else {
            conn.Write(output)
        }
        
        conn.Write([]byte("$ "))
    }
}