Go语言的变量、函数、Socks5代理服务器示例详解

// 声明并初始化一个变量var m int = 10// 声明初始化多个变量var i, j, k = 1, 2, 3// 多个变量的声明(注意小括号的使用)var( no int name string)// 声明时不指明类型，通过初始化值来推导var b = true // bool型// := 隐含声明变量并赋值str := "mimvp.com"  // 等价于var str string = "mimvp.com"

// = 使用必须使用先var声明例如：var aa = 100// 或var b = 100// 或var c int = 100// := 是声明并赋值，并且系统自动推断类型，不需要var关键字d := 100// Go中有一个特殊的变量下划线"_" 表示任何赋给它的值将被丢弃_, Ret:= 2, 3  // 2赋值被丢弃

const (  constName1 [type] = val1  constName2 [type] = val2 ) 

/*** mimvp.com* 2017.1.20*/// 声明当前文件所属的包名，main是一个可独立运行的包，编译后会生成可执行文件 package main import "fmt" // 导入包 var id = 123456 /* id2 := 654321 // 在函数外用 := ，编译时会出现错误，局部变量声明应在函数内部// non-declaration statement outside function body */ const PI = 3.14  // 常量声明// 每个可独立运行的程序，都包含入口函数 main ，与其他语言相同，但无参数和返回值 func main() {  var num int  num = 100  fmt.Println(num)  // 输出 100  var num1, num2 int  num1, num2 = 1, 2  fmt.Println(num1, num2) // 输出 1 2  var no1, no2 = 3, 4  fmt.Println(no1, no2)  // 输出 3 4  n1, n2 := 5, 6  fmt.Println(n1, n2)  // 输出 5 6  _, n := 7, 8  fmt.Println(n)    // 输出 8  var (   key1 string   key2 string  )  key1, key2 = "k1", "k2"  fmt.Println(key1, key2) // 输出 k1 k2  var (   a = 9   b = 10  )  fmt.Println(a, b)   // 输出 9 10  fmt.Println(id)   // 输出 123456  fmt.Println(PI)   // 输出 3.14  /*  PI = 3.1415  // 改变常量的值，编译会出现错误  // cannot assign to PI  // cannot use 3.1415 (type float64) as type ideal in assignment  */ }

func GetMsg(i int) (str string) { fmt.Println(i) str = "hello mimvp.com" return str}

<span style="color:#0000FF;">vim mimvp_func.go</span>func GetMsg(i int) (str string, err string) { fmt.Println(i) str = "hello mimvp.com" err = "no err" return str, err}func main() { fmt.Println(GetMsg(100))}

$ go build mimvp_func.go $ ./mimvp_func   100hello mimvp.com no err

func ReadFile(filePath string)(){ file.Open(filePath) defer file.Close()   if true {  file.Read() } else {  return false }}

package mainimport "fmt"func main() { f() fmt.Println("Returned normally from f.")}func f() { defer func() {  if r := recover(); r != nil {   fmt.Println("Recovered in f", r)  } }() fmt.Println("Calling g.") g(0) fmt.Println("Returned normally from g.")}func g(i int) { if i > 3 {  fmt.Println("Panicking!")  panic(fmt.Sprintf("%v", i)) } defer fmt.Println("Defer in g", i) fmt.Println("Printing in g", i) g(i + 1)}

$ ./mimvp-try-catch   Calling g.Printing in g 0Printing in g 1Printing in g 2Printing in g 3Panicking!Defer in g 3Defer in g 2Defer in g 1Defer in g 0Recovered in f 4Returned normally from f.

package mainimport ( "net" "fmt" "io" "bytes" "encoding/binary")type Methods struct{ ver, nmethods uint8 methods uint8}type sock5cmd struct{ ver, cmd, rsv, atyp uint8 dst [255]uint8}type proxyCoder struct { conn net.Conn}func (c *proxyCoder) readMethods() Methods { var m Methods b := make([]byte, 1024) n, err := c.conn.Read(b) if err != nil && err != io.EOF { panic(err) } buf := bytes.NewBuffer(b[0:n]) err = binary.Read(buf, binary.LittleEndian, &m.ver) if err != nil {  fmt.Println("binary.Read failed:", err) } err = binary.Read(buf, binary.LittleEndian, &m.nmethods) if err != nil {  fmt.Println("binary.Read failed:", err) } err = binary.Read(buf, binary.BigEndian, &m.methods) if err != nil {  fmt.Println("binary.Read failed:", err) } return m}func (c *proxyCoder) returnMethod() { buf := make([]byte, 2) buf[0] = 5 buf[1] = 0 c.conn.Write(buf) fmt.Println(buf)}func (c *proxyCoder) serve() { buf := make([]byte, 128) n, err := c.conn.Read(buf) if err != nil && err != io.EOF { panic(err) } fmt.Println(buf[:n]) var s string var t string var i int if(buf[3] == 3){//domail  for i = 4; i < n-2; i++ {   s += fmt.Sprintf("%c", buf[i])  } } else {//ip4 or ip6  s += fmt.Sprintf("%d", buf[4])  for i = 5; i < n-2; i++ {   s += fmt.Sprintf(".%d", buf[i])  } } p := make([]byte, 2) var port uint16 p[1] = buf[n-1] p[0] = buf[n-2] b := bytes.NewBuffer(p) err = binary.Read(b, binary.BigEndian, &port) if err != nil {  fmt.Println("binary.Read failed:", err) } s += fmt.Sprintf(":%d", port) switch buf[1] {  case 1://TCP   t = "tcp"  case 2://BIND  case 3://UDP   t = "udp" } conn, err := net.Dial(t, s) if err != nil {  fmt.Printf("%s connect error %s/n", t, s)  buf[1] = 4  c.conn.Write(buf[:n])  c.conn.Close()  return } buf[1] = 0 c.conn.Write(buf[:n]) fmt.Printf("%s connect success %s/n", t, s) go serv(conn, c.conn) go serv(c.conn, conn)}func serv(in net.Conn, out net.Conn){ b := make([]byte, 10240) for ;;{  n, err := in.Read(b)  if( err != nil ){   fmt.Printf("close/n")   in.Close()   out.Close()   return  }  fmt.Printf("serv %d/n", n)  out.Write(b[:n]); }}type Proxy struct {}func NewProxy() *Proxy { return &Proxy{}}var DefaultProxy = NewProxy()func (p *Proxy) ProxyConn(conn net.Conn ){ c := &proxyCoder{conn} m := c.readMethods() fmt.Println(m) c.returnMethod() c.serve()}func handleConnection(conn net.Conn){ buf := make([]byte, 1024) n, err := conn.Read(buf) if err != nil && err != io.EOF { panic(err) } fmt.Println(buf[:n]) //answer buf[0] = 5 buf[1] = 0 conn.Write(buf[:2]) fmt.Println(buf[:2]) //serve n, err = conn.Read(buf) if err != nil && err != io.EOF { panic(err) } fmt.Println(buf[:n]) conn.Close()}func main() { ln, err := net.Listen("tcp", ":1080") if err != nil {  fmt.Printf("bind error/n")  return } for {  conn, err := ln.Accept()  if err != nil {   fmt.Printf("accept error/n")   continue  }  go DefaultProxy.ProxyConn(conn)  //go handleConnection(conn) }}