package main 
import (
 "fmt"
 "net"
 "log"
 "os"
)
 
func main() {
 addr := "0.0.0.0:8787"
 tcpAddr, err := net.ResolveTCPAddr("tcp",addr)
 if err != nil {
 log.Fatalf("net.ResovleTCPAddr fail:%s", addr) //等價于print err后，再os.Exit(1)
 }
 
 listener, err := net.ListenTCP("tcp", tcpAddr)
 if err != nil {
 log.Fatalf("listen %s fail: %s", addr, err)
 }else {
 
 log.Println("rpc listening", addr)
 }
 
 for {
 conn, err := listener.Accept()
 if err != nil {
 log.Println("listener.Accept error:", err)
 continue
 }
 
 go handle_Client(conn)
 }
} 
 
func handle_Client(conn net.Conn) {
 defer conn.Close()
 
 var write_buffer []byte = []byte("ok")
 read_buffer := make([]byte, 128)
 
 n, err1 := conn.Read(read_buffer)
 if err1 != nil {
 fmt.Println("ser Read failed:", err1)
 os.Exit(1)
 }
 
 m, err2 := conn.Write(write_buffer)
 if err2 != nil {
 fmt.Println("ser send error:", err2)
 os.Exit(1)
 }
 
 fmt.Println("ser read cli send data count:", n, "msg:", string(read_buffer))
 fmt.Println("ser send data to cli count:", m, "msg:", string(write_buffer)) 
 fmt.Println("********one connetion end*********")
}

package main 
import (
 "fmt"
 "net"
 "os"
 "time"
)
 
func main() {
 conn, err := net.Dial("tcp", "127.0.0.1:8787")
 if err != nil {
 fmt.Println("dial failed:", err)
 os.Exit(1)
 }
 defer conn.Close() 
 
 var write_buffer []byte = []byte("Hi,server. I'm client.")
 read_buffer := make([]byte, 128)
 
 start_time := time.Now()
 n, err2 := conn.Write(write_buffer)
 if err2 != nil {
 fmt.Println("cli send error:", err2)
 os.Exit(1)
 }
 
 m, err1 := conn.Read(read_buffer)
 if err1 != nil {
 fmt.Println("cli Read failed:", err1)
 os.Exit(1)
 }
 response_time := time.Since(start_time)
 RTT_time := float64(response_time.Nanoseconds()) / 1e+06 //ns-->ms 
 fmt.Println(RTT_time) 
 fmt.Println("cli send data to ser count:", n, "msg:", string(write_buffer)) 
 fmt.Println("cli read ser data count:", m, "msg:", string(read_buffer))
}

func hand_conn(conn net.Conn) ([]byte){
  defer conn.Close()
  //clientarr := conn.RemoteAddr() //獲取連接到的對像的IP地址
  result := bytes.NewBuffer(nil)
  var buf [512]byte
  for {
    n, err := conn.Read(buf[0:])
    result.Write(buf[0:n])
    if err != nil {
      if err == io.EOF {
       break
      }
    }
  }
  //explan_rec_infos(string(result.Bytes()))
  return result.Bytes()
}
func main() {
 fmt.Println("Hello World! go server")
  server, err := net.Listen("tcp", ":9993")
  if err == nil { //若果err為nil，則成功創建
    index := 1
    for {
      index++
      con, _ := server.Accept()
      fmt.Println("有一個客戶連接" , index)
      hand_conn(con)
    }
  } else {
    return
  }
}