FTPClient.go

/*
FTPClient

本程序协议支持三种命令
DIR			返回当前目录下文件和文件夹
CD <dir>	进入子目录
PWD			请求当前工作目录
*/
package main

import (
	"bufio"
	"bytes"
	"fmt"
	"net"
	"os"
	"strings"
)

// string used by the user interface
const (
	uiDir  = "dir"
	uiCd   = "cd"
	uiPwd  = "pwd"
	uiQuit = "quit"
)

const (
	DIR = "DIR"
	CD  = "CD"
	PWD = "PWD"
)

func main() {
	if len(os.Args) != 2 {
		fmt.Println("Usage: ", os.Args[0], " host:port")
		os.Exit(1)
	}

	host := os.Args[1]

	conn, err := net.Dial("tcp", host)
	checkError(err)

	// 标准输入设备
	reader := bufio.NewReader(os.Stdin)
	for {
		// 读取一行
		line, err := reader.ReadString('\n')
		line = strings.TrimRight(line, "\t\r\n")
		if err != nil {
			break
		}

		// 切分命令和参数
		strs := strings.SplitN(line, " ", 2)
		switch strs[0] {
		case uiDir:
			dirRequest(conn)
		case uiCd:
			if len(strs) != 2 {
				fmt.Println("cd <dir>")
				continue
			}
			fmt.Println("CD \"", strs[1], "\"")
			cdRequest(conn, strs[1])
		case uiPwd:
			pwdRequest(conn)
		case uiQuit:
			conn.Close()
			os.Exit(0)
		default:
			fmt.Println("Unknow command")
		}
	}
}

func dirRequest(conn net.Conn) {
	conn.Write([]byte(DIR + " "))

	var buf [512]byte
	result := bytes.NewBuffer(nil)
	for {
		n, _ := conn.Read(buf[0:])
		result.Write(buf[0:n])
		length := result.Len()
		contents := result.Bytes()
		if string(contents[length-4:]) == "\r\n\r\n" {
			fmt.Println(string(contents[0 : length-4]))
			return
		}
	}
}

func cdRequest(conn net.Conn, dir string) {
	conn.Write([]byte(CD + " " + dir))

	var response [512]byte
	n, _ := conn.Read(response[0:])
	s := string(response[0:n])
	if s != "OK" {
		fmt.Println("Failed to change dir")
	} else {
		fmt.Println("OK")
	}
}

func pwdRequest(conn net.Conn) {
	conn.Write([]byte(PWD))

	var response [512]byte
	n, _ := conn.Read(response[0:])
	s := string(response[0:n])

	fmt.Println("Current dir \"" + s + "\"")
}

func checkError(err error) {
	if err != nil {
		fmt.Println("Fatal error ", err.Error())
		os.Exit(1)
	}
}