diff --git a/cmd/mtwebmapper/forwardupdates.go b/cmd/mtwebmapper/forwardupdates.go
index 4477214..470398c 100644
--- a/cmd/mtwebmapper/forwardupdates.go
+++ b/cmd/mtwebmapper/forwardupdates.go
@@ -4,23 +4,109 @@
 
 package main
 
-import "net/http"
+import (
+	"bytes"
+	"encoding/json"
+	"log"
+	"net/http"
+
+	"github.com/gorilla/websocket"
+)
 
 type websocketForwarder struct {
+	upgrader    *websocket.Upgrader
+	register    chan *connection
+	unregister  chan *connection
+	broadcast   chan map[xz]bool
+	connections map[*connection]bool
+}
+
+type connection struct {
+	ws   *websocket.Conn
+	send chan []byte
 }
 
 func newWebsocketForwarder() *websocketForwarder {
-	return &websocketForwarder{}
+	upgrader := &websocket.Upgrader{ReadBufferSize: 512, WriteBufferSize: 2048}
+	return &websocketForwarder{
+		upgrader:    upgrader,
+		register:    make(chan *connection),
+		unregister:  make(chan *connection),
+		broadcast:   make(chan map[xz]bool),
+		connections: make(map[*connection]bool)}
 }
 
 func (wsf *websocketForwarder) run() {
-	// TODO: Implement me!
+	for {
+		select {
+		case c := <-wsf.register:
+			wsf.connections[c] = true
+		case c := <-wsf.unregister:
+			if _, ok := wsf.connections[c]; ok {
+				delete(wsf.connections, c)
+				close(c.send)
+			}
+		case changes := <-wsf.broadcast:
+			if len(wsf.connections) == 0 {
+				continue
+			}
+			// Do the JSON encoding this late to save
+			// some CPU cyles if no client is connected.
+			xzs := make([]xz, 0, len(changes))
+			for xz := range changes {
+				xzs = append(xzs, xz)
+			}
+			var buf bytes.Buffer
+			encoder := json.NewEncoder(&buf)
+			if err := encoder.Encode(xzs); err != nil {
+				log.Printf("encoding changes failed: %s\n", err)
+				continue
+			}
+			msg := buf.Bytes()
+			for c := range wsf.connections {
+				select {
+				case c.send <- msg:
+				default:
+					delete(wsf.connections, c)
+					close(c.send)
+				}
+			}
+		}
+	}
 }
 
 func (wsf *websocketForwarder) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
-	// TODO: Implement me!
+	ws, err := wsf.upgrader.Upgrade(rw, r, nil)
+	if err != nil {
+		log.Printf("Cannot upgrade to websocket: %s\n", err)
+		return
+	}
+	c := &connection{ws: ws, send: make(chan []byte, 8)}
+	wsf.register <- c
+	defer func() { wsf.unregister <- c }()
+	go c.writer()
+	c.reader()
 }
 
 func (wsf *websocketForwarder) BaseTilesUpdated(changes map[xz]bool) {
-	// TODO: Implement me!
+	wsf.broadcast <- changes
+}
+
+func (c *connection) writer() {
+	defer c.ws.Close()
+	for msg := range c.send {
+		if c.ws.WriteMessage(websocket.TextMessage, msg) != nil {
+			break
+		}
+	}
+}
+
+func (c *connection) reader() {
+	defer c.ws.Close()
+	for {
+		// Just read the message and ignore it.
+		if _, _, err := c.ws.ReadMessage(); err != nil {
+			break
+		}
+	}
 }