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udp_demo_handler.go
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/
udp_demo_handler.go
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package main
import (
"fmt"
"html/template"
"net"
"net/http"
"net/url"
"time"
)
type UDPDemoResultPage struct {
Stylesheet template.HTML
TestRequestMessage string
TestResponseMessage string
}
var udpDemoResultPageTemplate string = `
<!DOCTYPE html>
<html lang="en">
<head>
<title>Frontend</title>
<meta charset="utf-8">
<meta http-equiv="X-UA-Compatible" content="IE=edge">
<meta name="viewport" content="width=device-width, initial-scale=1">
{{.Stylesheet}}
</head>
<body>
<div class="container">
<div class="header clearfix navbar navbar-inverse">
<div class="container">
<h3>Frontend Sample App</h3>
</div>
</div>
<div class="jumbotron">
<p>You sent the message: <code>{{.TestRequestMessage}}</code> </p>
<p>Backend UDP server replied: <code>{{.TestResponseMessage}}</code> </p>
</div>
</div>
</body>
</html>
`
type UDPDemoHandler struct{}
func doUDPTest(backendAddress, requestMessage string) (string, error) {
serverAddr, err := net.ResolveUDPAddr("udp", backendAddress)
if err != nil {
return "", fmt.Errorf("resolve udp address: %s", err)
}
connection, err := net.DialUDP("udp", nil, serverAddr)
if err != nil {
return "", fmt.Errorf("dial udp: %s", err)
}
err = connection.SetDeadline(time.Now().Add(5 * time.Second))
if err != nil {
return "", fmt.Errorf("set deadline: %s", err)
}
defer connection.Close()
_, err = connection.Write([]byte(requestMessage))
if err != nil {
return "", fmt.Errorf("write udp data: %s", err)
}
buffer := make([]byte, 1024)
numBytesReceived, _, err := connection.ReadFromUDP(buffer)
if err != nil {
return "", fmt.Errorf("read udp data: %s", err)
}
responseMessage := string(buffer[:numBytesReceived])
return responseMessage, nil
}
func (u *UDPDemoHandler) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
queryParams, err := url.ParseQuery(req.URL.RawQuery)
if err != nil {
panic(err)
}
backendURL := queryParams["url"][0]
requestMessage := queryParams["message"][0]
responseMessage, err := doUDPTest(backendURL, requestMessage)
if err != nil {
template := template.Must(template.New("formPage").Parse(errorPageTemplate))
err = template.Execute(resp, ErrorPage{
Stylesheet: stylesheet,
Error: err,
})
if err != nil {
panic(err)
}
return
}
theTemplate := template.Must(template.New("udpTestPage").Parse(udpDemoResultPageTemplate))
err = theTemplate.Execute(resp, UDPDemoResultPage{
Stylesheet: stylesheet,
TestRequestMessage: requestMessage,
TestResponseMessage: responseMessage,
})
if err != nil {
panic(err)
}
}