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* Standalone signaling server for the Nextcloud Spreed app.
* Copyright (C) 2017 struktur AG
* @author Joachim Bauch <>
* @license GNU AGPL version 3 or any later version
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* GNU Affero General Public License for more details.
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <>.
package signaling
import (
const (
initialConnectInterval = time.Second
maxConnectInterval = 8 * time.Second
type NatsMessage struct {
SendTime time.Time `json:"sendtime"`
Type string `json:"type"`
Message *ServerMessage `json:"message,omitempty"`
Room *BackendServerRoomRequest `json:"room,omitempty"`
Permissions []Permission `json:"permissions,omitempty"`
Id string `json:"id"`
type NatsSubscription interface {
Unsubscribe() error
type NatsClient interface {
Subscribe(subject string, ch chan *nats.Msg) (NatsSubscription, error)
Publish(subject string, message interface{}) error
PublishNats(subject string, message *NatsMessage) error
PublishMessage(subject string, message *ServerMessage) error
PublishBackendServerRoomRequest(subject string, message *BackendServerRoomRequest) error
Decode(msg *nats.Msg, v interface{}) error
// The NATS client doesn't work if a subject contains spaces. As the room id
// can have an arbitrary format, we need to make sure the subject is valid.
// See "" for a similar report.
func GetEncodedSubject(prefix string, suffix string) string {
return prefix + "." + base64.StdEncoding.EncodeToString([]byte(suffix))
type natsClient struct {
nc *nats.Conn
conn *nats.EncodedConn
func NewNatsClient(url string) (NatsClient, error) {
if url == ":loopback:" {
log.Println("No NATS url configured, using internal loopback client")
return NewLoopbackNatsClient()
client := &natsClient{}
var err error, err = nats.Connect(url,
interrupt := make(chan os.Signal, 1)
signal.Notify(interrupt, os.Interrupt)
defer signal.Stop(interrupt)
delay := initialConnectInterval
timer := time.NewTimer(delay)
// The initial connect must succeed, so we retry in the case of an error.
for err != nil {
log.Printf("Could not create connection (%s), will retry in %s", err, delay)
select {
case <-interrupt:
return nil, fmt.Errorf("interrupted")
case <-timer.C:
// Retry connection
delay = delay * 2
if delay > maxConnectInterval {
delay = maxConnectInterval
}, err = nats.Connect(url)
log.Printf("Connection established to %s (%s)",,
// All communication will be JSON based.
client.conn, _ = nats.NewEncodedConn(, nats.JSON_ENCODER)
return client, nil
func (c *natsClient) Close() {
func (c *natsClient) onClosed(conn *nats.Conn) {
log.Println("NATS client closed", conn.LastError())
func (c *natsClient) onDisconnected(conn *nats.Conn) {
log.Println("NATS client disconnected")
func (c *natsClient) onReconnected(conn *nats.Conn) {
log.Printf("NATS client reconnected to %s (%s)", conn.ConnectedUrl(), conn.ConnectedServerId())
func (c *natsClient) Subscribe(subject string, ch chan *nats.Msg) (NatsSubscription, error) {
return, ch)
func (c *natsClient) Publish(subject string, message interface{}) error {
return c.conn.Publish(subject, message)
func (c *natsClient) PublishNats(subject string, message *NatsMessage) error {
return c.Publish(subject, message)
func (c *natsClient) PublishMessage(subject string, message *ServerMessage) error {
msg := &NatsMessage{
SendTime: time.Now(),
Type: "message",
Message: message,
return c.PublishNats(subject, msg)
func (c *natsClient) PublishBackendServerRoomRequest(subject string, message *BackendServerRoomRequest) error {
msg := &NatsMessage{
SendTime: time.Now(),
Type: "room",
Room: message,
return c.PublishNats(subject, msg)
func (c *natsClient) Decode(msg *nats.Msg, v interface{}) error {
return c.conn.Enc.Decode(msg.Subject, msg.Data, v)