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main.go
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main.go
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package main
import (
"context"
"fmt"
"net/http"
"os"
"os/signal"
"time"
ws "github.com/josephwoodward/go-websocket-server/websocket"
)
type server struct {
srv *http.Server
ws *ws.WsUpgradeResult
}
func main() {
mux := http.NewServeMux()
const port = ":8082"
server := &server{
srv: &http.Server{Addr: port, Handler: mux},
}
mux.HandleFunc("/ws", func(w http.ResponseWriter, r *http.Request) {
wsRes, err := ws.Upgrade(w, r)
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
}
for {
frame := ws.Frame{}
// read first 2 bytes (16 bits)
head, err := wsRes.Read(2)
if err != nil {
fmt.Printf(err.Error())
w.WriteHeader(http.StatusInternalServerError)
}
// https://datatracker.ietf.org/doc/html/rfc6455#section-5.2
// 1 byte (8 bits) is the smallest addressable unit of memory
// work out flags with first 4 bits, remaing 4 bits are opcode
// 129 = 1000 0001
// Fragment is first bit so target first bit to determind fragment
// 10000000 is 128 decimal, 0x80 hexidecimal
// 0x00 = 0000000
// fmt.Printf("The value is: %t", (10000001&10000000) == 00000000) = false
// 10000001
// 10000000 = 0
frame.IsFragment = (head[0] & 0x80) == 0x00
frame.Opcode = ws.WsOpCode(head[0] & 0x0F)
frame.Reserved = (head[0] & 0x70)
frame.IsMasked = (head[1] & 0x80) == 0x80
frame.Length = uint64(head[1] & 0x7F)
frame.MaskingKey, err = wsRes.Read(4)
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
}
payload, err := wsRes.Read(int(frame.Length)) // possible data loss
if err != nil {
w.WriteHeader(http.StatusInternalServerError)
}
for i := uint64(0); i < frame.Length; i++ {
payload[i] ^= frame.MaskingKey[i%4]
}
frame.Payload = payload
switch frame.Opcode {
case ws.WsPingMessage, ws.WsPongMessage, ws.WsCloseMessage:
fmt.Print("ping")
case ws.WsTextMessage:
fmt.Printf("payload: %s", frame.Payload)
default:
break
}
}
// server.ws = wsRes
})
go func() {
fmt.Printf("starting server on port %s\n", port)
if err := server.srv.ListenAndServe(); err != nil {
fmt.Printf("failed to start server: %s\n", err)
}
}()
stop := make(chan os.Signal, 1)
signal.Notify(stop, os.Interrupt)
<-stop
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
if err := server.srv.Shutdown(ctx); err != nil {
fmt.Printf("failed to shutdown server: %s\n", err)
}
}