go http.Handler

http1

package main

import (
    "log"
    "net/http"
    "fmt"
)

func main() {
    db:=database{"shoes":,"socks":}
    log.Fatal(http.ListenAndServe("localhost:5000",db))
}
type dollars float32

func (d dollars) String() string {
    return fmt.Sprintf("$%.2f",d)
}
type database map[string]dollars

func (db database) ServeHTTP(w http.ResponseWriter, req *http.Request) {
    for item,price:=range db{
        fmt.Fprintf(w,"%s: %s\n",item,price)
    }
}

打开浏览器：http://localhost:5000/

http2

package main

import (
    "fmt"
    "net/http"
    "log"
)

func main() {
    db:=database{"shoes":,"socks":}
    mux:=http.NewServeMux()
    mux.Handle("/list",http.HandlerFunc(db.list))
    mux.Handle("/price",http.HandlerFunc(db.price))
    log.Fatal(http.ListenAndServe("localhost:5000",mux))
}
type database map[string]dollars
type dollars float32

func (d dollars) String() string {
    return fmt.Sprintf("$%.2f",d)
}
func (db database) list(w http.ResponseWriter, req *http.Request) {
    for item,price:=range db{
        fmt.Fprintf(w,"%s: %s\n",item,price)
    }
}
func (db database) price(w http.ResponseWriter,req *http.Request)  {
    item:=req.URL.Query().Get("item")
    price,ok:=db[item]
    if !ok{
        w.WriteHeader(http.StatusNotFound)
        fmt.Fprintf(w,"no such item: %q\n",item)
        return
    }
    fmt.Fprintf(w,"%s\n",price)
}

打开浏览器：http://localhost:5000/price?item=socks

clock1

package main

import (
    "net"
    "io"
    "time"
    "log"
)

func main() {
    listener,err:=net.Listen("tcp","localhost:8000")
    if err!=nil{
        log.Fatal(err)
    }
    for{
        conn,err:=listener.Accept()
        if err!=nil{
            log.Print(err)
            continue
        }
        handleConn(conn)
    }
}

func handleConn(c net.Conn) {
    defer c.Close()
    for{
        _,err:=io.WriteString(c,time.Now().Format("15:04:05\r\n"))
        if err!=nil{
            return
        }
        time.Sleep(*time.Second)
    }
}

运行clock1，打开cmd，使用telnet localhost 8000 进行连接

或者使用下面的程序

netcat1

package main

import (
    "io"
    "log"
    "net"
    "os"
)

func main() {
    conn,err:=net.Dial("tcp","localhost:8000")
    if err!=nil{
        log.Fatal(err)
    }
    defer conn.Close()
    mustCopy(os.Stdout,conn)
}

func mustCopy(dst io.Writer, src io.Reader) {
    if _,err:=io.Copy(dst,src);err!=nil{
        log.Fatal(err)
    }
}

为了让服务器支持并发，只需要在handleConn上添加一个go

clock2

    for{
        conn,err:=listener.Accept()
        if err!=nil{
            log.Print(err)
            continue
        }
        go handleConn2(conn)
    }