afcapel/go.mod

## go.mod
module main

go 1.17

require github.com/gorilla/websocket v1.4.2 // indirect

## server.go
package main

import (
	"flag"
	"fmt"
	"html/template"
	"log"
	"net/http"
	"strings"

	"github.com/gorilla/websocket"
)

var addr = flag.String("addr", "localhost:8080", "http service address")

var upgrader = websocket.Upgrader{
	EnableCompression: true,
}

func echo(w http.ResponseWriter, r *http.Request) {
	c, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
		log.Print("upgrade:", err)
		return
	}
	defer c.Close()
	for {
		mt, message, err := c.ReadMessage()
		if err != nil {
			log.Println("read:", err)
			break
		}
		log.Printf("recv: %d bytes", len(message))
		err = c.WriteMessage(mt, message)
		if err != nil {
			log.Println("write:", err)
			break
		}
	}
}

func home(w http.ResponseWriter, r *http.Request) {
	homeTemplate.Execute(w, "ws://"+r.Host+"/echo")
}

func main() {
	flag.Parse()
	log.SetFlags(0)
	http.HandleFunc("/echo", echo)
	http.HandleFunc("/", home)
	log.Fatal(http.ListenAndServe(*addr, nil))
}

var longMessage = strings.Repeat("All work and no play makes Jack a dull boy\n", 1024*72)
var templateString = fmt.Sprintf(`
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<script>
window.addEventListener("load", function(evt) {
    var output = document.getElementById("output");
    var input = document.getElementById("input");
    var ws;
    var print = function(message) {
        var d = document.createElement("div");
        d.textContent = message;
        output.appendChild(d);
        output.scroll(0, output.scrollHeight);
    };
    document.getElementById("open").onclick = function(evt) {
        if (ws) {
            return false;
        }
        ws = new WebSocket("{{.}}");
        ws.onopen = function(evt) {
            print("OPEN");
        }
        ws.onclose = function(evt) {
            print("CLOSE");
            ws = null;
        }
        ws.onmessage = function(evt) {
            print("RECEIVED: " + evt.data.length + " chars");
        }
        ws.onerror = function(evt) {
            print("ERROR: " + evt.data);
        }
        return false;
    };
    document.getElementById("send").onclick = function(evt) {
        if (!ws) {
            return false;
        }
        print("SEND: " + input.value.length + " chars");
        ws.send(input.value);
        return false;
    };
    document.getElementById("close").onclick = function(evt) {
        if (!ws) {
            return false;
        }
        ws.close();
        return false;
    };
});
</script>
</head>
<body>
<p>Click "Open" to create a connection to the server,
"Send" to send a message to the server and "Close" to close the connection.
You can change the message and send multiple times.
</p>

<form>
	<p>
		<button id="open">Open</button>
	</p>
	<p>
		<button id="close">Close</button>
	</p>

	<p>
		<textarea id="input">%s</textarea>
	</p>

	<p>
		<button id="send">Send</button>
	</p>
</form>

<div id="output" style="max-height: 70vh;overflow-y: scroll;"></div>
</body>
</html>
`, longMessage)

var homeTemplate = template.Must(template.New("").Parse(templateString))
	module main

	go 1.17

	require github.com/gorilla/websocket v1.4.2 // indirect
	package main

	import (
	"flag"
	"fmt"
	"html/template"
	"log"
	"net/http"
	"strings"

	"github.com/gorilla/websocket"
	)

	var addr = flag.String("addr", "localhost:8080", "http service address")

	var upgrader = websocket.Upgrader{
	EnableCompression: true,
	}

	func echo(w http.ResponseWriter, r *http.Request) {
	c, err := upgrader.Upgrade(w, r, nil)
	if err != nil {
	log.Print("upgrade:", err)
	return
	}
	defer c.Close()
	for {
	mt, message, err := c.ReadMessage()
	if err != nil {
	log.Println("read:", err)
	break
	}
	log.Printf("recv: %d bytes", len(message))
	err = c.WriteMessage(mt, message)
	if err != nil {
	log.Println("write:", err)
	break
	}
	}
	}

	func home(w http.ResponseWriter, r *http.Request) {
	homeTemplate.Execute(w, "ws://"+r.Host+"/echo")
	}

	func main() {
	flag.Parse()
	log.SetFlags(0)
	http.HandleFunc("/echo", echo)
	http.HandleFunc("/", home)
	log.Fatal(http.ListenAndServe(*addr, nil))
	}

	var longMessage = strings.Repeat("All work and no play makes Jack a dull boy\n", 1024*72)
	var templateString = fmt.Sprintf(`
	<!DOCTYPE html>
	<html>
	<head>
	<meta charset="utf-8">
	<script>
	window.addEventListener("load", function(evt) {
	var output = document.getElementById("output");
	var input = document.getElementById("input");
	var ws;
	var print = function(message) {
	var d = document.createElement("div");
	d.textContent = message;
	output.appendChild(d);
	output.scroll(0, output.scrollHeight);
	};
	document.getElementById("open").onclick = function(evt) {
	if (ws) {
	return false;
	}
	ws = new WebSocket("{{.}}");
	ws.onopen = function(evt) {
	print("OPEN");
	}
	ws.onclose = function(evt) {
	print("CLOSE");
	ws = null;
	}
	ws.onmessage = function(evt) {
	print("RECEIVED: " + evt.data.length + " chars");
	}
	ws.onerror = function(evt) {
	print("ERROR: " + evt.data);
	}
	return false;
	};
	document.getElementById("send").onclick = function(evt) {
	if (!ws) {
	return false;
	}
	print("SEND: " + input.value.length + " chars");
	ws.send(input.value);
	return false;
	};
	document.getElementById("close").onclick = function(evt) {
	if (!ws) {
	return false;
	}
	ws.close();
	return false;
	};
	});
	</script>
	</head>
	<body>
	<p>Click "Open" to create a connection to the server,
	"Send" to send a message to the server and "Close" to close the connection.
	You can change the message and send multiple times.
	</p>

	<form>
	<p>
	<button id="open">Open</button>
	</p>
	<p>
	<button id="close">Close</button>
	</p>

	<p>
	<textarea id="input">%s</textarea>
	</p>

	<p>
	<button id="send">Send</button>
	</p>
	</form>

	<div id="output" style="max-height: 70vh;overflow-y: scroll;"></div>
	</body>
	</html>
	`, longMessage)

	var homeTemplate = template.Must(template.New("").Parse(templateString))