Web sockets over TLS

A web socket can be built above a secure TLS socket. We discussed in Chapter 8: HTTP how to use a TLS socket using the certificates from Chapter 7: Security. That is used unchanged for web sockets. that is, we use http.ListenAndServeTLS instead of http.ListenAndServe.

Here is the echo server using TLS

/* EchoServer
 */
package main

import (
    "golang.org/x/net/websocket"
    "fmt"
    "net/http"
    "os"
)

func Echo(ws *websocket.Conn) {
    fmt.Println("Echoing")

    for n := 0; n < 10; n++ {
        msg := "Hello  " + string(n+48)
        fmt.Println("Sending to client: " + msg)
        err := websocket.Message.Send(ws, msg)
        if err != nil {
            fmt.Println("Can't send")
            break
        }

        var reply string
        err = websocket.Message.Receive(ws, &reply)
        if err != nil {
            fmt.Println("Can't receive")
            break
        }
        fmt.Println("Received back from client: " + reply)
    }
}

func main() {

    http.Handle("/", websocket.Handler(Echo))
    err := http.ListenAndServeTLS(":12345", "jan.newmarch.name.pem",
        "private.pem", nil)
    checkError(err)
}

func checkError(err error) {
    if err != nil {
        fmt.Println("Fatal error ", err.Error())
        os.Exit(1)
    }
}

The client is the same echo client as before. All that changes is the url, which uses the "wss" scheme instead of the "ws" scheme:

EchoClient wss://localhost:12345/

Conclusion

The web sockets standard is nearing completion and no major changes are anticipated. This will allow HTTP user agents and servers to set up bi-directional socket connections and should make certain interaction styles much easier. Go has nearly complete support for web sockets.