websocket.go

package main

import (
	"flag"
	"log"
	"os"
	"os/signal"
	"time"

	"github.com/gorilla/websocket"
)

var addr = "wss://api.radarrelay.com/0x/v0/ws"

func main() {
	flag.Parse()
	log.SetFlags(0)

	timeoutDuration := 2 * time.Minute

	interrupt := make(chan os.Signal, 1)
	signal.Notify(interrupt, os.Interrupt)

	c, _, err := websocket.DefaultDialer.Dial(addr, nil)
	if err != nil {
		log.Fatal("dial:", err)
	} else {
		log.Println("Connected to server")
	}

	c.SetPongHandler(func(str string) error {
		log.Println("pong received", str)
		return nil
	})

	defer c.Close()

	done := make(chan struct{})

	go func() {
		defer c.Close()
		defer close(done)
		for {
			c.SetReadDeadline(time.Now().Add(timeoutDuration))
			_, message, err := c.ReadMessage()
			if err != nil {
				log.Println("read:", err)
				return
			}
			if len(message) >= 2 {
				message = message[2:]
			}
			log.Printf("recv: %s", message)
		}
	}()

	ticker := time.NewTicker(10 * time.Second)
	defer ticker.Stop()

	for {
		select {
		case _ = <-ticker.C:
			err := c.WriteMessage(websocket.PingMessage, []byte{})
			if err != nil {
				log.Println("write:", err)
				return
			} else {
				log.Println("ping sent")
			}
		case <-interrupt:
			log.Println("interrupt")
			// To cleanly close a connection, a client should send a close
			// frame and wait for the server to close the connection.
			err := c.WriteMessage(
				websocket.CloseMessage,
				websocket.FormatCloseMessage(websocket.CloseNormalClosure, ""))
			if err != nil {
				log.Println("write close:", err)
				return
			}
			select {
			case <-done:
			case <-time.After(time.Second):
			}
			c.Close()
			return
		}
	}
}