Implementation of tcp automatic reconnection example tutorial

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Operating system: CentOS 6.9_x64

go language version: 1.8.3

Problem description

There is an existing tcp client program that needs to regularly retrieve data from the server, but needs to automatically reconnect due to various reasons (network instability, etc.).

Test server sample code:

/*
tcp server for test

*/


package main

import (
  "fmt"
  "net"
  "os"
  "strings"
  "time"
)

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

func handleClient(conn net.Conn) {
  conn.SetReadDeadline(time.Now().Add(3 * time.Minute))
  request := make([]byte,1024)
  defer conn.Close()

  for {
    recv_len,err := conn.Read(request)
    if err != nil {
      fmt.Println(err)
      break
    }
    if recv_len == 0 {
      break
    }
    recvData := strings.TrimSpace(string(request[:recv_len]))
    fmt.Println("recv_len : ",recv_len)
    fmt.Println("recv_data : " + recvData)
    daytime := time.Now().String()
    conn.Write([]byte(daytime + "\n"))
    request = make([]byte,1024)
  }
}

func main() {
  bindInfo := ":12345"
  tcpAddr,err := net.ResolveTCPAddr("tcp4",bindInfo)
  checkError(err)
  listener,err := net.ListenTCP("tcp",tcpAddr)
  checkError(err)
  for {
    cc,err := listener.Accept()
    if err != nil {
      continue
    }
    go handleClient(cc)
  }
}

Solution

/*
tcp client with reconnect

*/

package main

import (
  "net"
  "fmt"
  "bufio"
  "time"
)

func doTask(conn net.Conn) {
  for {
    fmt.Fprintf(conn,"test msg\n")
    msg,err := bufio.NewReader(conn).ReadString('\n')
    if err != nil {
      fmt.Println("recv data error")
      break
    }else{
      fmt.Println("recv msg : ",msg)
    }
    time.Sleep(1 * time.Second)
  }

}

func main() {
  hostInfo := "127.0.0.1:12345"

  for {
    conn,err := net.Dial("tcp",hostInfo)
    fmt.Print("connect (",hostInfo)
    if err != nil {
      fmt.Println(") fail")
    }else{
      fmt.Println(") ok")
      defer conn.Close()
      doTask(conn)
    }
    time.Sleep(3 * time.Second)
  }
}

Running effect:

##

[root@local t1]# ./tcpClient1
connect (127.0.0.1:12345) ok
recv msg : 2017-06-12 21:10:32.110977137 +0800 CST

recv msg : 2017-06-12 21:10:33.111868746 +0800 CST

recv data error
connect (127.0.0.1:12345) fail
connect (127.0.0.1:12345) fail
connect (127.0.0.1:12345) ok
recv msg : 2017-06-12 21:10:43.117203432 +0800 CST

recv msg : 2017-06-12 21:10:44.11853427 +0800 CST

Discussion

Here is just a simple sample code that implements tcp automatic reconnection.

Okay, that’s all, I hope it helps.

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