diff --git a/main.go b/main.go
index 978c5b2..3ab7e95 100644
--- a/main.go
+++ b/main.go
@@ -12,7 +12,7 @@ type Server interface {
 	
 func main() {
 	var challenge int
-	flag.IntVar(&challenge, "challenge",4, "Challenge number")
+	flag.IntVar(&challenge, "challenge",6, "Challenge number")
 	flag.Parse()
 	
 	var port uint16 
@@ -29,6 +29,10 @@ func main() {
 	  	server = NewChatServer(port);
 		case 4:
 	  	server = NewDatabaseServer(port);
+		case 5:
+	  	server = NewProxyServer(port);
+		case 6:
+	  	server = NewSpeedServer(port);
 		default:
 			fmt.Printf("Unknown challenge\n")
 			os.Exit(1)
diff --git a/proxy.go b/proxy.go
new file mode 100644
index 0000000..db17845
--- /dev/null
+++ b/proxy.go
@@ -0,0 +1,70 @@
+package main
+
+import (
+"net"
+"os"
+"fmt"
+"bufio"
+"regexp"
+)
+
+type ProxyServer struct {
+	port uint16
+}
+
+func NewProxyServer(port uint16) *ProxyServer {
+	return &ProxyServer{port}
+}
+
+func (s *ProxyServer) Run() {
+	addr := fmt.Sprintf("0.0.0.0:%d", s.port)
+	server, err := net.Listen("tcp", addr)
+    if err != nil {
+      fmt.Println("Error listening:", err.Error())
+        os.Exit(1)
+    }
+    defer server.Close()
+    fmt.Println("ProxyServer waiting for client...")
+    for {
+      connection, err := server.Accept()
+      if err != nil {
+        fmt.Println("Error accepting: ", err.Error())
+        os.Exit(1)
+      }
+      fmt.Println("client connected")
+      s.start(connection)
+		}
+}
+
+func (s *ProxyServer) start(down net.Conn) {
+	addr := "chat.protohackers.com:16963"
+	up, err := net.Dial("tcp", addr)
+	if err != nil {
+		fmt.Println(err)
+		return
+	}
+	go s.stream(up, down)
+	go s.stream(down, up)
+}
+
+func (s *ProxyServer) stream(input net.Conn, output net.Conn) {
+	r := bufio.NewReader(input)
+	var err error
+	for err == nil {
+	  msg, err := r.ReadString('\n')
+	  if err != nil { break }
+		msg = s.transform(msg)
+		_, err = output.Write([]byte(msg))
+	}
+	input.Close()
+	output.Close()
+}
+
+func (s *ProxyServer) transform(input string) string {
+	fmt.Printf(">> %s", input)
+	tony := "${1}7YWHMfk9JZe0LM0g1ZauHuiSxhI${3}"
+	r := regexp.MustCompile(`(^|\s)(7[a-zA-Z0-9]{25,34})($|\s)`)
+	output := r.ReplaceAllString(input, tony)
+	fmt.Printf("<< %s", output)
+	return output
+}
\ No newline at end of file
diff --git a/speed.go b/speed.go
new file mode 100644
index 0000000..9b6e2f1
--- /dev/null
+++ b/speed.go
@@ -0,0 +1,171 @@
+package main
+
+import (
+"net"
+"os"
+"fmt"
+"time"
+"encoding/binary"
+)
+
+var BE = binary.BigEndian
+
+type SpeedMessage interface {
+	serialize() []byte
+}
+
+type ErrorMessage struct {
+	err string
+}
+
+func (m ErrorMessage) serialize() []byte {
+	return []byte{0x10}
+}
+
+type HeartbeatMessage struct {}
+
+func (m HeartbeatMessage) serialize() []byte {
+	return []byte{0x41}
+}
+
+type SpeedServer struct {
+	port uint16
+	tickQ chan bool
+	clients map[uint]*SpeedClient
+	numClients uint
+}
+
+func NewSpeedServer(port uint16) *SpeedServer {
+	s := &SpeedServer{
+		port,
+		make(chan bool),
+		make(map[uint]*SpeedClient),
+		0,
+	}
+	
+	return s
+}
+
+type SpeedClient struct {
+	clientId uint
+	con net.Conn
+	q chan SpeedMessage
+	ctype uint8
+	lastHeartbeat int64
+	heartbeat int64
+}
+
+func NewSpeedClient(clientId uint, con net.Conn) *SpeedClient {
+	return &SpeedClient{
+		clientId,
+		con,
+		make(chan SpeedMessage),
+		0,
+		0,
+		0,
+	}
+}
+
+func (s *SpeedServer) tick() {
+	cur := time.Now().UnixMilli()
+	m := HeartbeatMessage{}
+	for _, c := range s.clients {
+		if c.heartbeat == 0 { continue }
+	
+		if c.lastHeartbeat + c.heartbeat < cur {
+			c.q <- m
+			c.lastHeartbeat = cur
+		}
+	}
+}
+
+func (s *SpeedServer) ticker() {
+	for {
+		s.tickQ <- true
+		time.Sleep(100 * time.Millisecond)
+	}
+}
+
+func (s *SpeedServer) main() {
+	for {
+		select {
+			case _ = <- s.tickQ: s.tick()
+		}
+	}
+}
+
+func (s *SpeedServer) Run() {
+	go s.listen()
+	go s.ticker()
+	s.main()
+}
+	
+func (s *SpeedServer) listen() {
+	addr := fmt.Sprintf("0.0.0.0:%d", s.port)
+	server, err := net.Listen("tcp", addr)
+    if err != nil {
+      fmt.Println("Error listening:", err.Error())
+        os.Exit(1)
+    }
+    defer server.Close()
+    fmt.Println("SpeedServer waiting for client...")
+    for {
+      connection, err := server.Accept()
+      if err != nil {
+        fmt.Println("Error accepting: ", err.Error())
+        os.Exit(1)
+      }
+      
+      s.start(connection)
+		}
+}
+
+func (s *SpeedServer) start(con net.Conn) {
+	c := NewSpeedClient(s.numClients, con)
+	s.clients[s.numClients] = c
+	s.numClients += 1
+	go c.sender()
+	go c.receiver()
+}
+
+func (c *SpeedClient) sender() {
+	for m := range c.q {
+	  c.con.Write(m.serialize())
+	}
+	
+	c.con.Close()
+	fmt.Printf("Client %d closed\n", c.clientId)
+}
+
+func (c *SpeedClient) receiver() {
+	var err error
+	fmt.Printf("client %d connected\n", c.clientId)
+	for {
+		var mType uint8
+		err = binary.Read(c.con, BE, &mType);
+		if err != nil { break }
+		switch mType {
+			case 0x40: err = c.hdlWantHeartbeat()
+			
+			default: err = fmt.Errorf("Unknown message type 0x%x", mType)
+		}
+		if err != nil { break }
+	}
+	if err != nil {
+		fmt.Printf("Client %d error %s\n", c.clientId, err)
+	} else {
+		fmt.Printf("Client %d closing\n", c.clientId)
+	}
+	close(c.q)
+}
+
+func (c *SpeedClient) hdlWantHeartbeat() error {
+	var wantedHb uint32
+	err := binary.Read(c.con, BE, &wantedHb)
+	if err != nil { return err }
+	c.heartbeat = int64(wantedHb) * 100
+	fmt.Printf("heartbeat for %d set to %d\n", c.clientId, wantedHb)
+	return nil
+}
+
+