gotunnel

Importable Go library that can be embedded inside your code to expose your locally running service to a public server. It serves as an open-source alternative to ngrok. And implements both server and client side.

Features

Handles TCP, HTTP and Websocket Connections
TLS Support w/ SSL Certificates on Server
In-memory cache for storing tunnels and sessions.
Connection Callbacks
Auto-Reconnect the Client
Authorized Whitelists and Blacklists for Hostnames

Coming Soon

Rate Limiting Per Connection
Load Balancer for the Server
SSH Tunnels
Public Key Authentication

Installation

go get -u github.com/gotunnel/gotunnel

Usage

Server

For a simple HTTP server, just supply the local port you want to expose.

log.Fatal(gotunnel.StartServer(&gotunnel.ServerConfig{
        Address:     ":80",
        InsecureSkipVerify: true,
}))

For an HTTPS Server, supply your SSL certificate and it's equivalent key files.

log.Fatal(gotunnel.StartServer(&gotunnel.ServerConfig{
        Address:     ":443",
        Certificate: "./server.crt",
        Key:         "./server.key",
}))

Authentication Middleware

On server side, you can supply a custom authentication function that will be executed when a new tunnel creation request is received by the server. It takes an HTTP request and returns an error.

For example, you can use it to authenticate the users who are requesting a new tunnel from your server.

func authenticate (r *http.Request) error {
    // perform authentication
}

log.Fatal(gotunnel.StartServer(&gotunnel.ServerConfig{
        Address:     ":80",
        Auth: authenticate,
}))

Callback Functions

These are specialized functions that if supplied, are triggered on specific client state changes.

For example, the OnConnection callback function is triggered once a new tunnel is successfully established.

log.Fatal(gotunnel.StartServer(&gotunnel.ServerConfig{
	Address:            ":5000",
	InsecureSkipVerify: true,
	Callbacks: gotunnel.Callbacks{
		OnConnection: func(w http.ResponseWriter, r *http.Request) error {
			w.Write([]byte("Hello World!"))
			return nil
		},
	},
}))

Client

Simple client, without listening for state changes for established tunnel. The token must be unique for every client-server tunnel you create. This token is also used as an identifier by the server to filter and proxy requests.

client := &gotunnel.ClientConfig{
    Address: "http://sub.example.com:80",
    Token:   "your_secret_token",

    // Local port to route incoming requests to
    Port:    "8080",
    InsecureSkipVerify: true,
}

if err := client.Connect(); err != nil {
    return err
}

For more professional debugging, you can attach a read-only go channel to receive real-time state change notifications.

state := make(chan *gotunnel.TunnelState)

client, _ := gotunnel.NewClient(&gotunnel.ClientConfig{
    Address: "https://sub.example.com:443",
    Token:   "your_secret_token",
    Port:    "8080",
    State:   state,
})

go func() {
    for {
        change := <-state
        if *change == gotunnel.Connecting {
            log.Println("Connecting")
        } else if *change == gotunnel.Connected {
            log.Println("Connected")
        } else if *change == gotunnel.Disconnected {
            log.Println("Disconnected")
        }
    }
}()

if err := client.Connect(); err != nil {
    return err
}

Client Auto-Reconnect

You can watch the gotunnel.Disconnected state change, and use it to re-connect your client to the server.

Example: Reconnect With Exponential Backoff

You can use a simple backoff library in golang like github.com/jpillora/backoff to attempt reconnection in exponential intervals.

state := make(chan *gotunnel.TunnelState)

client, _ := gotunnel.NewClient(&gotunnel.Client{
    Address: "https://sub.example.com:443",
    Token:   "your_secret_token",
    Port:    "8080",
    State:   state,
})

b := &backoff.Backoff{
    Max:    5 * time.Minute,
}

var err error

go func() {
    for {
        change := <-state
        if *change == gotunnel.Disconnected {
            time.Sleep(b.Duration())
            err = client.Connect()
        }
    }
}()

if err = client.Connect(); err != nil {
    return err
}