CODEWITHSUNDEEP
javascriptgowebsocket
HowToGo
HowToGo

Reputation: 367

Pushing changes to client using websockets Golang

I have been trying to push changes done on server side using websockets in Golang.

I have achived what i wanted by this code

Server side code:

package main

import (
   "golang.org/x/net/websocket"
   "fmt"
   "net/http"
   "os"
   "bufio"
)

type chat struct {
    message string
}

func (ms *chat) Echo(ws *websocket.Conn) {
    var reply string
    for {
         if reply !=  ms.message {
         websocket.Message.Send(ws, ms.message)
         }
         websocket.Message.Receive(ws, reply)
    }
}

func NewMessage(s *string){
   reader := bufio.NewReader(os.Stdin)
   for {
       fmt.Print("Enter text: ")
       *s, _ = reader.ReadString('\n')
       }
   }

func main() {
   myString := chat{"Welcome"}
   go NewMessage(&myString.message)
   http.Handle("/", websocket.Handler(myString.Echo))
   http.ListenAndServe(":1234", nil)
}

Client side code:

<html>
<body>
<script type="text/javascript">
    var exampleSocket = new WebSocket("ws://127.0.0.1:1234");

    exampleSocket.onopen = function (event) {
    console.log("connected");
    };

    exampleSocket.onmessage = function (event) {
        console.log(event.data);
        exampleSocket.send(event.data)
        document.getElementById("p1").innerHTML = event.data;
    }


</script>
<h1>WebSockets</h1>
<form>
    <p id="p1" value="Hello, world!"/>
</form>

The problem with above code is repeatedly sending ms.message as if reply != ms.message does not work. Simply var reply string value is not being changed by websocket.Message.Receive(ws, reply).

I have tried passing reply as a pointer but it does not update value on the client side dynamically.

Here is how server side would look like after the change:

package main

import (
   "golang.org/x/net/websocket"
   "fmt"
   "net/http"
   "os"
   "bufio"
)

type chat struct {
    message string
}

func (ms *chat) Echo(ws *websocket.Conn) {
    var reply string
    for {
         if reply !=  ms.message {
         websocket.Message.Send(ws, ms.message)
         }
         websocket.Message.Receive(ws, &reply)
    }
}

func NewMessage(s *string){
   reader := bufio.NewReader(os.Stdin)
   for {
       fmt.Print("Enter text: ")
       *s, _ = reader.ReadString('\n')
       }
   }

func main() {
   myString := chat{"Welcome"}
   go NewMessage(&myString.message)
   http.Handle("/", websocket.Handler(myString.Echo))
   http.ListenAndServe(":1234", nil)
}

This code does not fit my expectations.

Is it possible to dynamically update string on clients side without sending value multiple times as it is being done in the example number 1?

Upvotes: 2

Views: 2136

Answers (1)

AESTHETICS
AESTHETICS

Reputation: 1049

Simply putting websocket.Message.Receive in the if statement fixes the problem.

package main

import (
   "golang.org/x/net/websocket"
   "fmt"
   "net/http"
   "os"
   "bufio"
)

type chat struct {
   message string
}

func (ms *chat) Echo(ws *websocket.Conn) {
   var reply string
      for {
         if reply !=  ms.message {
            websocket.Message.Send(ws, ms.message)
            websocket.Message.Receive(ws, &reply)
         }

      }
}

func NewMessage(s *string){
reader := bufio.NewReader(os.Stdin)
for {
   fmt.Print("Enter text: ")
   *s, _ = reader.ReadString('\n')
  }
}

func main() {
   myString := chat{"Welcome"}
   go NewMessage(&myString.message)
   http.Handle("/", websocket.Handler(myString.Echo))
   http.ListenAndServe(":1234", nil)
}

Upvotes: 2

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