/
main.go
125 lines (104 loc) · 3 KB
/
main.go
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package main
import (
"context"
"fmt"
"io"
"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 initial 8 bits (2 bytes). This will give us enough information to decide how we handle the frame.
head := make([]byte, 2)
if _, err = wsRes.Bufrw.Read(head); err != nil {
fmt.Print("breaking head read")
break
}
if len(head) == 0 {
continue
}
// https://datatracker.ietf.org/doc/html/rfc6455#section-5.2
// 1 byte (8 bits) is the smallest addressable unit of memory
// first 4 bits are flags with 3 reserved
// first 1 bit is Fragment, using 128 binary representation as a bool flag via bitwise operator
// 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.IsFinal = (head[0] & 0x80) == 0x00
frame.Opcode = ws.WsOpCode(head[0] & 0x0F)
fmt.Printf("For byte '%d', Opcode is %d\n", head[0], frame.Opcode)
frame.Reserved = (head[0] & 0x70)
frame.IsMasked = (head[1] & 0x80) == 0x80
frame.Length = uint64(head[1] & 0x7F)
maskingKey := make([]byte, 4)
if _, err = wsRes.Bufrw.Read(maskingKey); err == io.EOF {
fmt.Print("breaking masking key")
break
}
frame.MaskingKey = maskingKey
payload := make([]byte, int(frame.Length))
if _, err = wsRes.Bufrw.Read(payload); err == io.EOF {
fmt.Print("breaking payload length")
break
}
for i := uint64(0); i < frame.Length; i++ {
payload[i] ^= frame.MaskingKey[i%4]
}
frame.Payload = payload
switch frame.Opcode {
case ws.WsCloseMessage:
fmt.Print("closing connection")
case ws.WsPingMessage, ws.WsPongMessage:
fmt.Print("ping / pong")
case ws.WsTextMessage:
fmt.Printf("received payload message: %s\n", string(frame.Payload))
f := ws.Frame{
IsFinal: true,
Opcode: ws.WsTextMessage,
IsMasked: false,
Payload: []byte("Hello Mike"),
}
wsRes.Write(f)
default:
break
}
}
})
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)
}
}