websockets and go
ascii
posted: Feb, 17th 2012 | jump to bottom
/*
A simple go program that demonstates websockets. To run it
1. build it with "go build ws.go" Tested with go version weekly.2012-02-14 +43cf9b39b647
2. run the program
3. point chrome to http://localhost:40000 Tested with chrome 17.0.963.56
4. type some key value pairs in the console of 2 and see them in the browser
The html content must be served by a server and cannot be loaded by a file.
This is because the web socket protocol must set the Origin property to
sth meaningful. Notice how elegantly a string is served by go using http
*/
package main
import (
"io"
"fmt"
"net/http"
"code.google.com/p/go.net/websocket"
)
type Item struct {
Key string
Val string
}
func ReadAndSendItems(ws *websocket.Conn) {
var key, val string
for {
fmt.Printf("key value: ")
_, err := fmt.Scan(&key, &val)
if err == io.EOF {
return
}
if err != nil && err != io.EOF {
panic(err)
}
websocket.JSON.Send(ws, Item{key, val})
}
}
func ItemsServer(ws *websocket.Conn) {
fmt.Println("opened connection")
ReadAndSendItems(ws)
ws.Close()
fmt.Println("closed connection")
}
func main() {
http.Handle("/items", websocket.Handler(ItemsServer))
http.Handle("/", page)
err := http.ListenAndServe(":40000", nil)
if err != nil {
panic("ListenAndServe: " + err.Error())
}
}
type Page string
func (p Page) ServeHTTP(rw http.ResponseWriter, req *http.Request) {
io.WriteString(rw, string(p))
}
var page Page = `<!DOCTYPE html>
<html>
<head>
<title>websockets in action</title>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.1/jquery.min.js"></script>
<script>
$(function() {
var ws = new WebSocket("ws://localhost:40000/items");
ws.onopen = function() {
$("#status").text("Current Items: Connected");
$("#items").show();
};
ws.onerror = function() {
$("#items").hide();
$("#status").text("Current Items: Connection Error");
};
ws.onclose = function() {
$("#items").hide();
$("#status").text("Current Items: Connection Closed");
};
ws.onmessage = function(msg) {
var item = JSON.parse(msg.data);
$("tbody").append("<tr><td>" + item.Key + "</td><td>" + item.Val + "</td></tr>");
}
});
</script>
</head>
<body>
<h1 id="status">Status</h1>
<table id="items" hidden="true">
<thead><tr><th>Key</th><th>Value</th></tr></thead>
<tbody></tbody>
</table>
</body>
</html>`
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