WebSocket

• WebSocket

Server

Client

Proxy

import (
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"

	"github.com/gin-gonic/gin"
	"github.com/gobwas/ws"
)

func WebsocketProxy(c *gin.Context) {
	connClient, _, _, err := ws.UpgradeHTTP(c.Request, c.Writer)
	if err != nil {
		c.Status(http.StatusInternalServerError)
		return
	}
	defer connClient.Close()

	u, _ := url.Parse("ws://websocket.default.svc.cluster.local:8080/ws")
	u.RawQuery = c.Request.URL.RawQuery

	dial := ws.Dialer{}
	dialHeader := http.Header{}
	dial.Header = ws.HandshakeHeaderHTTP(dialHeader)

	connServer, _, _, err := dial.Dial(c.Request.Context(), u.String())
	if err != nil {
		c.Status(http.StatusInternalServerError)
		return
	}
	defer connServer.Close()

	errClient := make(chan error, 1)
	errServer := make(chan error, 1)

	go func() {
		for {
			header, err := ws.ReadHeader(connClient)
			if err != nil {
				errClient <- err
			}

			payload := make([]byte, header.Length)
			_, err = io.ReadFull(connClient, payload)
			if err != nil {
				errClient <- err
			}

			if err := ws.WriteHeader(connServer, header); err != nil {
				errServer <- err
			}

			if _, err := connServer.Write(payload); err != nil {
				errServer <- err
			}

			if header.OpCode == ws.OpClose {
				errServer <- errConnectionClose
			}
		}
	}()

	go func() {
		for {
			header, err := ws.ReadHeader(connServer)
			if err != nil {
				errServer <- err
			}

			payload := make([]byte, header.Length)
			_, err = io.ReadFull(connServer, payload)
			if err != nil {
				errServer <- err
			}

			if err := ws.WriteHeader(connClient, header); err != nil {
				errClient <- err
			}

			if _, err := connClient.Write(payload); err != nil {
				errClient <- err
			}

			if header.OpCode == ws.OpClose {
				errClient <- errConnectionClose
			}
		}
	}()

	select {
	case err = <-errClient:
		err = fmt.Errorf("client: %w", err)
	case err = <-errServer:
		err = fmt.Errorf("server: %w", err)
	}

	if errors.Is(err, errConnectionClose) {
		return
	} else {
		c.Status(http.StatusInternalServerError)
		c.Error(err)
	}
}