ws

Example about websocket server and notifications from server.

package main

import (
	"context"
	"fmt"
	"net"
	"net/http"

	"nhooyr.io/websocket"

	"gitlab.com/pjrpc/pjrpc/v2/client"
	"gitlab.com/pjrpc/pjrpc/ws"
)

func main() {
	ctx := context.Background()
	address := "localhost:8080"
	endpoint := fmt.Sprintf("ws://%s/ws", address)

	conf := &ws.Config{
		Accept: func(w http.ResponseWriter, r *http.Request) (accepted bool) {
			return true // You can validate http request here.
		},
	}

	wsServer := ws.NewServerWebsocket(conf)

	clients := make(chan *client.AsyncClient)

	wsServer.OnNewConnection = func(_ context.Context, conn net.Conn) bool {
		fmt.Println("Got a new connection")

		cl := client.NewAsyncClient(conn)

		// Don't call cl.Listen() when your server already listens this connection.

		clients <- cl

		// You can return false if you don't want to accept this connection.
		return true
	}

	wsServer.OnCloseConnection = func(_ context.Context, conn net.Conn) {
		// Just remove client from your notification logic.
		// You don't need close notification client here (cl.Close).
	}

	mux := http.NewServeMux()
	mux.Handle("/ws", wsServer)

	go func() {
		err := http.ListenAndServe(address, mux)
		if err != nil {
			fmt.Println("http.ListenAndServe:", err)
		}
	}()

	clientGotMessage := make(chan string)

	go func() {
		c, _, err := websocket.Dial(ctx, endpoint, nil)
		if err != nil {
			fmt.Println("websocket.Dial:", err)
			return
		}

		mt, message, err := c.Read(ctx)
		if err != nil {
			fmt.Println("c.Read:", err)
			return
		}

		if mt != websocket.MessageText {
			fmt.Println("wrong message type:", mt)
			return
		}

		clientGotMessage <- string(message)
	}()

	// Waiting for a new client.
	cl := <-clients

	err := cl.Invoke(ctx, "", "notify", "string as parameter", nil)
	if err != nil {
		fmt.Println("client.Invoke:", err)
		return
	}

	// Waiting for a message that got the client.
	fmt.Println(<-clientGotMessage)

}

Output:

Got a new connection
{"jsonrpc":"2.0","method":"notify","params":"string as parameter"}