golang tcp automatic reconnection method

Operating system: CentOS 6.9_x64

go version: 1.8.3

Problem description

There is an tcp client program that needs to fetch data from the server on a regular basis, but needs automatic reconnection 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)
  }
}

The 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)
  }
}

Operation 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

discuss

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

Well, that's all. I hope it helped.