Golang concurrently reading from a tcp connectoin - go

Question

I am having some issue with a Go project. The code is way too big to copy and paste so I will try to explain as well as I can.
My program first connects to a TCP server, then it starts a goroutine passing as argument the connection object.
What I'm trying to achieve is having the client to read infinitely from the tcp connection while at the same time to take user input and communicate to the server by sending a retrieving data. I've tried using another goroutine but the program blocks whenever trying to retrieve data from the server.
Here is a reproduction of the error on go playground.
https://play.golang.org/p/OD5ozCRmy_4 server
https://play.golang.org/p/t1r_BAQM-jn client
Basically whenever the client tries to read from the connection it gets stuck.
Thank you for your help.

Answer 1

You should use channel
here is a sample which can receive some connection and each connection could send data as wish
package tcp
import (
"bufio"
"fmt"
"net"
"strconv"
"../log"
"../config"
"../controllers"
h "../helpers"
)
type msgFormat struct {
text []byte
net.Conn
}
var accounts = make(map[net.Conn]int)
var conns = make(chan net.Conn)
var dconns = make(chan net.Conn)
var msgs = make(chan msgFormat)
var i int
//Init is first point
func Init() {
startserver()
for {
select {
case conn := <-conns:
handleconnect(conn)
case msg := <-msgs:
go handlemsg(msg)
case dconn := <-dconns:
handlediscounect(dconn)
}
}
}
func handlemsg(incomemsg msgFormat) {
logger.Log.Println(string(incomemsg.text))
resp, err := controllers.Do(incomemsg.text)
if err != nil {
logger.Log.Println(err.Error())
}
strLen := []byte(h.Lpad(string(fmt.Sprintf("%v", len(resp))), "0", 4))
//
fresponse := append(strLen, resp...)
incomemsg.Write(fresponse)
logger.Log.Println("response is %v" , string(fresponse))
}
func startserver() {
conf := config.GetConfigInstance()
ln, err := net.Listen(conf.SERVER.Nettype, conf.SERVER.Address)
if err != nil {
logger.Log.Println(err.Error())
}
logger.Log.Printf("server is serving at %v", conf.SERVER.Address)
go func() {
for {
conn, err := ln.Accept()
if err != nil {
logger.Log.Println(err.Error())
}
conns <- conn
}
}()
}
func readdate(conn net.Conn, i int) {
for {
rd := bufio.NewReader(conn)
dataLen := make([]byte, 4)
_, err := rd.Read(dataLen)
if err != nil {
break
}
intLen, _ := strconv.Atoi(string(dataLen))
data := make([]byte, intLen)
_, err = rd.Read(data)
if err != nil {
break
}
msgs <- msgFormat{data, conn}
}
dconns <- conn
}
func handleconnect(newconnection net.Conn) {
accounts[newconnection] = i
i++
// if addr , ok := newconnection.RemoteAddr().str
logger.Log.Printf("Action: Client_Connected %v is connected via %v \n", i, newconnection.RemoteAddr().(*net.TCPAddr).IP)
go readdate(newconnection, i)
}
func handlediscounect(disconnection net.Conn) {
logger.Log.Printf("Action: Client_Disconnected %v / %v is gone\n", accounts[disconnection] + 1, disconnection.RemoteAddr().(*net.TCPAddr).IP)
delete(accounts, disconnection)
}