diff --git a/cmd/conn_unix.go b/cmd/conn_unix.go
new file mode 100644
index 0000000..3b156e2
--- /dev/null
+++ b/cmd/conn_unix.go
@@ -0,0 +1,70 @@
+// Copied with modifications from https://github.com/insomniacslk/dhcp/blob/master/dhcpv4/server4/conn_unix.go (under BSD-3-Clause license)
+//go:build !windows
+
+package cmd
+
+import (
+	"errors"
+	"fmt"
+	"net"
+	"os"
+
+	"github.com/adrianokf/go-dhcp/pkg/types"
+	"golang.org/x/sys/unix"
+)
+
+// NewIPv4UDPConn returns a UDP connection bound to both the interface and port
+// given based on a IPv4 DGRAM socket. The UDP connection allows broadcasting.
+//
+// The interface must already be configured.
+func NewIPv4UDPConn(iface string, addr *net.UDPAddr) (*net.UDPConn, error) {
+	fd, err := unix.Socket(unix.AF_INET, unix.SOCK_DGRAM, unix.IPPROTO_UDP)
+	if err != nil {
+		return nil, fmt.Errorf("cannot get a UDP socket: %v", err)
+	}
+	f := os.NewFile(uintptr(fd), "")
+	// net.FilePacketConn dups the FD, so we have to close this in any case.
+	defer f.Close()
+
+	// Allow broadcasting.
+	if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_BROADCAST, 1); err != nil {
+		return nil, fmt.Errorf("cannot set broadcasting on socket: %v", err)
+	}
+	// Allow reusing the addr to aid debugging.
+	if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEADDR, 1); err != nil {
+		return nil, fmt.Errorf("cannot set reuseaddr on socket: %v", err)
+	}
+	// Allow reusing the port to aid debugging and testing.
+	if err := unix.SetsockoptInt(fd, unix.SOL_SOCKET, unix.SO_REUSEPORT, 1); err != nil {
+		return nil, fmt.Errorf("cannot set reuseport on socket: %v", err)
+	}
+	if len(iface) != 0 {
+		// Bind directly to the interface.
+		if err := unix.BindToDevice(fd, iface); err != nil {
+			return nil, fmt.Errorf("cannot bind to interface %s: %v", iface, err)
+		}
+	}
+
+	if addr == nil {
+		addr = &net.UDPAddr{Port: types.ServerPort}
+	}
+	// Bind to the port.
+	saddr := unix.SockaddrInet4{Port: addr.Port}
+	if addr.IP != nil && addr.IP.To4() == nil {
+		return nil, fmt.Errorf("wrong address family (expected v4) for %s", addr.IP)
+	}
+	copy(saddr.Addr[:], addr.IP.To4())
+	if err := unix.Bind(fd, &saddr); err != nil {
+		return nil, fmt.Errorf("cannot bind to port %d: %v", addr.Port, err)
+	}
+
+	conn, err := net.FilePacketConn(f)
+	if err != nil {
+		return nil, err
+	}
+	udpconn, ok := conn.(*net.UDPConn)
+	if !ok {
+		return nil, errors.New("BUG: incorrect socket type, expected UDP")
+	}
+	return udpconn, nil
+}
diff --git a/cmd/root.go b/cmd/root.go
index 3d08fbb..4161f06 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -11,20 +11,22 @@ import (
 	"github.com/adrianokf/go-dhcp/pkg/leases"
 	"github.com/adrianokf/go-dhcp/pkg/messages"
 	"github.com/adrianokf/go-dhcp/pkg/types"
+	"github.com/adrianokf/go-dhcp/pkg/util"
 	"github.com/spf13/cobra"
 	"go.uber.org/zap"
 )
 
 var listenInterface string
 
-var manager = leases.NewLeaseManager()
+type Handler struct {
+	conn         *net.UDPConn
+	leaseManager leases.LeaseManager
+}
 
 var magic = [4]byte{0x63, 0x82, 0x53, 0x63}
 
 func parseOptions(data []byte) messages.Options {
-	s := zap.S()
 	i := 0
-
 	options := make(messages.Options)
 
 out:
@@ -32,11 +34,11 @@ out:
 		code := messages.OptionCode(data[i])
 		switch code {
 		case messages.OptionEnd:
-			s.Debug("Found END option at offset ", i)
+			zap.S().Debug("Found END option at offset ", i)
 			break out
 
 		case messages.OptionPad:
-			s.Debug("Found padding option at offset ", i)
+			zap.S().Debug("Found padding option at offset ", i)
 			i += 1
 			continue
 		}
@@ -44,12 +46,12 @@ out:
 		size := int(data[i+1])
 		payload := data[i+2 : i+2+size]
 
-		s.Debugf("code=%d, size=%d, payload=%x", code, size, payload)
+		zap.S().Debugf("code=%d, size=%d, payload=%x", code, size, payload)
 		options[code] = messages.Option{Code: code, Data: data[i+1 : i+2+size]}
 		i += size + 2
 	}
 
-	s.Debugf("Parsed options: ", options)
+	zap.S().Debugf("Parsed options: ", options)
 	return options
 }
 
@@ -108,7 +110,18 @@ func prepareAck(request messages.DhcpMessage, lease leases.Lease) messages.DhcpM
 // sendMessage transmits a DHCP message with options via a UDP connection
 // The end option (code 255) is automatically appended and does not need to
 // be passed explicitly.
-func sendMessage(conn *net.UDPConn, message messages.DhcpMessage, options []messages.Option) error {
+func (h Handler) sendMessage(remote *net.UDPAddr, message messages.DhcpMessage, options []messages.Option) error {
+	// Send packets for 0.0.0.0 to broadcast address (255.255.255.255) instead
+	var destination *net.UDPAddr
+	if remote.IP.IsUnspecified() {
+		destination = &net.UDPAddr{
+			IP:   net.ParseIP("255.255.255.255"),
+			Port: types.ClientPort,
+		}
+	} else {
+		destination = remote
+	}
+
 	buf := make([]byte, 0)
 	w := bytes.NewBuffer(buf)
 	err := binary.Write(w, binary.BigEndian, message)
@@ -127,16 +140,16 @@ func sendMessage(conn *net.UDPConn, message messages.DhcpMessage, options []mess
 		}
 	}
 
-	// Automatically add END option, so the caller doesn't
-	// need to specificy it for every invocation.
+	// Automatically add END option, so the caller doesn't need to specify it for every invocation.
 	err = w.WriteByte(byte(messages.OptionEnd))
 	if err != nil {
 		return err
 	}
 
 	msg := w.Bytes()
-	zap.S().Debug("Msg", msg)
-	_, err = conn.Write(msg)
+	zap.S().Debugf("Local addr: %s, remote addr: %s ", h.conn.LocalAddr(), destination)
+	zap.S().Debug("Msg data: ", msg)
+	_, err = h.conn.WriteToUDP(msg, destination)
 	if err != nil {
 		return err
 	}
@@ -144,21 +157,14 @@ func sendMessage(conn *net.UDPConn, message messages.DhcpMessage, options []mess
 	return nil
 }
 
-func handleOffer(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
+func (h Handler) sendOffer(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
 	s := zap.S()
 
-	lease, err := manager.Request(dhcp.Xid, dhcp.Chaddr)
+	lease, err := h.leaseManager.Request(dhcp.Xid, dhcp.Chaddr)
 	if err != nil {
 		panic(err)
 	}
 	offer := prepareOffer(dhcp, *lease)
-	localAddr, _ := net.ResolveUDPAddr("udp", "172.17.0.1:68")
-	clientAddr, _ := net.ResolveUDPAddr("udp", "255.255.255.255:68")
-	conn, err := net.DialUDP("udp", localAddr, clientAddr)
-	if err != nil {
-		panic(err)
-	}
-	defer conn.Close()
 
 	s.Info("Sending DHCPOFFER...")
 	options := []messages.Option{
@@ -167,14 +173,14 @@ func handleOffer(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
 			Data: []byte{1, byte(messages.MessageTypeOffer)},
 		},
 	}
-	sendMessage(conn, offer, options)
+	h.sendMessage(remote, offer, options)
 	return nil
 }
 
-func handleAck(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
+func (h Handler) sendAck(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
 	s := zap.S()
 
-	lease, err := manager.Lookup(dhcp.Xid)
+	lease, err := h.leaseManager.Lookup(dhcp.Xid)
 	if err != nil {
 		panic(err)
 	}
@@ -188,31 +194,23 @@ func handleAck(dhcp messages.DhcpMessage, remote *net.UDPAddr) error {
 		},
 		{
 			Code: messages.OptionIPAddressLeaseTime,
-			Data: append([]byte{4}, u32tob(3600)...),
+			Data: append([]byte{4}, util.U32ToByte(3600)...),
 		},
 	}
 	s.Debug("Options: ", options)
 
-	localAddr, _ := net.ResolveUDPAddr("udp", "172.17.0.1:68")
-	clientAddr, _ := net.ResolveUDPAddr("udp", "255.255.255.255:68")
-	conn, err := net.DialUDP("udp", localAddr, clientAddr)
-	if err != nil {
-		panic(err)
-	}
-	defer conn.Close()
-
 	s.Info("Sending DHCPACK")
-	sendMessage(conn, ack, options)
+	h.sendMessage(remote, ack, options)
 
-	lease, err = manager.Request(dhcp.Xid, dhcp.Chaddr)
+	lease, err = h.leaseManager.Request(dhcp.Xid, dhcp.Chaddr)
 	if err != nil {
 		return err
 	}
-	s.Debug("Found lease", lease)
+	s.Debug("Found lease: ", lease)
 	return nil
 }
 
-func handleMsg(data []byte, remote *net.UDPAddr) {
+func (h Handler) handleMsg(data []byte, remote *net.UDPAddr) {
 	s := zap.S()
 
 	s.Debugf("Connection from client %v", remote.IP)
@@ -222,7 +220,7 @@ func handleMsg(data []byte, remote *net.UDPAddr) {
 	binary.Read(reader, binary.BigEndian, &dhcp)
 	dhcp.Debug(s)
 
-	if dhcp.Magic != [4]byte{0x63, 0x82, 0x53, 0x63} {
+	if dhcp.Magic != magic {
 		panic("Invalid DHCP magic field")
 	}
 
@@ -236,10 +234,10 @@ func handleMsg(data []byte, remote *net.UDPAddr) {
 
 	switch messages.MessageType(dhcpMsgType.Data[1]) {
 	case messages.MessageTypeDiscover:
-		go handleOffer(dhcp, remote)
+		go h.sendOffer(dhcp, remote)
 
 	case messages.MessageTypeRequest:
-		go handleAck(dhcp, remote)
+		go h.sendAck(dhcp, remote)
 	}
 }
 
@@ -249,7 +247,7 @@ func runServer(interfaceName string) {
 		zap.L().Debug("Listening on all interfaces")
 		addr, _ = net.ResolveUDPAddr("udp4", ":67")
 	} else {
-		zap.S().Debugf("Listening on interface %s", interfaceName)
+		zap.S().Debug("Listening on interface ", interfaceName)
 		iface, err := net.InterfaceByName(interfaceName)
 		if err != nil {
 			panic(err)
@@ -275,17 +273,28 @@ func runServer(interfaceName string) {
 			}
 		}
 		if ip == nil {
-			zap.S().Panicf("No IPv4 address associated with interface %s", interfaceName)
+			zap.S().Panic("No IPv4 address associated with interface ", interfaceName)
 		}
-		fmt.Printf("%+v\n", ip)
-		addr, _ = net.ResolveUDPAddr("udp4", ip.String()+":67")
+		addr, _ = net.ResolveUDPAddr("udp4", ":67")
+	}
+
+	var conn *net.UDPConn
+	var err error
+	if interfaceName != "all" {
+		conn, err = NewIPv4UDPConn(interfaceName, addr)
+	} else {
+		conn, err = net.ListenUDP("udp4", addr)
 	}
-	conn, err := net.ListenUDP("udp4", addr)
 	if err != nil {
 		panic(err)
 	}
 	defer conn.Close()
 
+	handler := Handler{
+		conn:         conn,
+		leaseManager: *leases.NewLeaseManager(),
+	}
+
 	zap.S().Infof("Listening for incoming connections on %s", addr.String())
 
 	for {
@@ -301,7 +310,7 @@ func runServer(interfaceName string) {
 			zap.S().Warn("Not a valid remote IP address: ", remote)
 			continue
 		}
-		go handleMsg(buf[0:rlen], remoteAddr)
+		go handler.handleMsg(buf[0:rlen], remoteAddr)
 	}
 }
 
diff --git a/go.mod b/go.mod
index 56ced9d..0faeedc 100644
--- a/go.mod
+++ b/go.mod
@@ -11,6 +11,6 @@ require (
 
 require (
 	github.com/spf13/cobra v1.8.0
-	go.uber.org/atomic v1.11.0 // indirect
 	go.uber.org/multierr v1.11.0 // indirect
+	golang.org/x/sys v0.16.0
 )
diff --git a/go.sum b/go.sum
index 7e35cc0..16c8d0e 100644
--- a/go.sum
+++ b/go.sum
@@ -1,6 +1,5 @@
-github.com/benbjohnson/clock v1.1.0 h1:Q92kusRqC1XV2MjkWETPvjJVqKetz1OzxZB7mHJLju8=
-github.com/benbjohnson/clock v1.1.0/go.mod h1:J11/hYXuz8f4ySSvYwY0FKfm+ezbsZBKZxNJlLklBHA=
 github.com/cpuguy83/go-md2man/v2 v2.0.3/go.mod h1:tgQtvFlXSQOSOSIRvRPT7W67SCa46tRHOmNcaadrF8o=
+github.com/creack/pty v1.1.9/go.mod h1:oKZEueFk5CKHvIhNR5MUki03XCEU+Q6VDXinZuGJ33E=
 github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
@@ -9,8 +8,7 @@ github.com/inconshreveable/mousetrap v1.1.0/go.mod h1:vpF70FUmC8bwa3OWnCshd2FqLf
 github.com/kr/pretty v0.1.0/go.mod h1:dAy3ld7l9f0ibDNOQOHHMYYIIbhfbHSm3C4ZsoJORNo=
 github.com/kr/pty v1.1.1/go.mod h1:pFQYn66WHrOpPYNljwOMqo10TkYh1fy3cYio2l3bCsQ=
 github.com/kr/text v0.1.0/go.mod h1:4Jbv+DJW3UT/LiOwJeYQe1efqtUx/iVham/4vfdArNI=
-github.com/pkg/errors v0.8.1 h1:iURUrRGxPUNPdy5/HRSm+Yj6okJ6UtLINN0Q9M4+h3I=
-github.com/pkg/errors v0.8.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/kr/text v0.2.0/go.mod h1:eLer722TekiGuMkidMxC/pM04lWEeraHUUmBw8l2grE=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
 github.com/russross/blackfriday/v2 v2.1.0/go.mod h1:+Rmxgy9KzJVeS9/2gXHxylqXiyQDYRxCVz55jmeOWTM=
@@ -19,24 +17,19 @@ github.com/spf13/cobra v1.8.0/go.mod h1:WXLWApfZ71AjXPya3WOlMsY9yMs7YeiHhFVlvLyh
 github.com/spf13/pflag v1.0.5 h1:iy+VFUOCP1a+8yFto/drg2CJ5u0yRoB7fZw3DKv/JXA=
 github.com/spf13/pflag v1.0.5/go.mod h1:McXfInJRrz4CZXVZOBLb0bTZqETkiAhM9Iw0y3An2Bg=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
-github.com/stretchr/testify v1.7.0 h1:nwc3DEeHmmLAfoZucVR881uASk0Mfjw8xYJ99tb5CcY=
+github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
+github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.1 h1:w7B6lhMri9wdJUVmEZPGGhZzrYTPvgJArz7wNPgYKsk=
+github.com/stretchr/testify v1.8.1/go.mod h1:w2LPCIKwWwSfY2zedu0+kehJoqGctiVI29o6fzry7u4=
 github.com/yuin/goldmark v1.3.5/go.mod h1:mwnBkeHKe2W/ZEtQ+71ViKU8L12m81fl3OWwC1Zlc8k=
-go.uber.org/atomic v1.7.0 h1:ADUqmZGgLDDfbSL9ZmPxKTybcoEYHgpYfELNoN+7hsw=
-go.uber.org/atomic v1.7.0/go.mod h1:fEN4uk6kAWBTFdckzkM89CLk9XfWZrxpCo0nPH17wJc=
-go.uber.org/atomic v1.11.0 h1:ZvwS0R+56ePWxUNi+Atn9dWONBPp/AUETXlHW0DxSjE=
-go.uber.org/atomic v1.11.0/go.mod h1:LUxbIzbOniOlMKjJjyPfpl4v+PKK2cNJn91OQbhoJI0=
-go.uber.org/goleak v1.1.11 h1:wy28qYRKZgnJTxGxvye5/wgWr1EKjmUDGYox5mGlRlI=
-go.uber.org/goleak v1.1.11/go.mod h1:cwTWslyiVhfpKIDGSZEM2HlOvcqm+tG4zioyIeLoqMQ=
 go.uber.org/goleak v1.2.0 h1:xqgm/S+aQvhWFTtR0XK3Jvg7z8kGV8P4X14IzwN3Eqk=
-go.uber.org/multierr v1.6.0 h1:y6IPFStTAIT5Ytl7/XYmHvzXQ7S3g/IeZW9hyZ5thw4=
-go.uber.org/multierr v1.6.0/go.mod h1:cdWPpRnG4AhwMwsgIHip0KRBQjJy5kYEpYjJxpXp9iU=
+go.uber.org/goleak v1.2.0/go.mod h1:XJYK+MuIchqpmGmUSAzotztawfKvYLUIgg7guXrwVUo=
+go.uber.org/multierr v1.10.0/go.mod h1:20+QtiLqy0Nd6FdQB9TLXag12DsQkrbs3htMFfDN80Y=
 go.uber.org/multierr v1.11.0 h1:blXXJkSxSSfBVBlC76pxqeO+LN3aDfLQo+309xJstO0=
 go.uber.org/multierr v1.11.0/go.mod h1:20+QtiLqy0Nd6FdQB9TLXag12DsQkrbs3htMFfDN80Y=
-go.uber.org/zap v1.21.0 h1:WefMeulhovoZ2sYXz7st6K0sLj7bBhpiFaud4r4zST8=
-go.uber.org/zap v1.21.0/go.mod h1:wjWOCqI0f2ZZrJF/UufIOkiC8ii6tm1iqIsLo76RfJw=
 go.uber.org/zap v1.26.0 h1:sI7k6L95XOKS281NhVKOFCUNIvv9e0w4BF8N3u+tCRo=
 go.uber.org/zap v1.26.0/go.mod h1:dtElttAiwGvoJ/vj4IwHBS/gXsEu/pZ50mUIRWuG0so=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
@@ -54,6 +47,8 @@ golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7w
 golang.org/x/sys v0.0.0-20201119102817-f84b799fce68/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210330210617-4fbd30eecc44/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20210510120138-977fb7262007/go.mod h1:oPkhp1MJrh7nUepCBck5+mAzfO9JrbApNNgaTdGDITg=
+golang.org/x/sys v0.16.0 h1:xWw16ngr6ZMtmxDyKyIgsE93KNKz5HKmMa3b8ALHidU=
+golang.org/x/sys v0.16.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
 golang.org/x/term v0.0.0-20201126162022-7de9c90e9dd1/go.mod h1:bj7SfCRtBDWHUb9snDiAeCFNEtKQo2Wmx5Cou7ajbmo=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/text v0.3.3/go.mod h1:5Zoc/QRtKVWzQhOtBMvqHzDpF6irO9z98xDceosuGiQ=
@@ -66,9 +61,6 @@ golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8T
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
 gopkg.in/check.v1 v1.0.0-20180628173108-788fd7840127/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v2 v2.2.8 h1:obN1ZagJSUGI0Ek/LBmuj4SNLPfIny3KsKFopxRdj10=
-gopkg.in/yaml.v2 v2.2.8/go.mod h1:hI93XBmqTisBFMUTm0b8Fm+jr3Dg1NNxqwp+5A1VGuI=
 gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
-gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b h1:h8qDotaEPuJATrMmW04NCwg7v22aHH28wwpauUhK9Oo=
-gopkg.in/yaml.v3 v3.0.0-20210107192922-496545a6307b/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
diff --git a/pkg/leases/leases.go b/pkg/leases/leases.go
index fe02d1e..604b922 100644
--- a/pkg/leases/leases.go
+++ b/pkg/leases/leases.go
@@ -1,8 +1,11 @@
 package leases
 
 import (
+	"encoding/json"
 	"errors"
 	"fmt"
+	"os"
+	"path/filepath"
 	"time"
 
 	"github.com/adrianokf/go-dhcp/pkg/types"
@@ -16,12 +19,14 @@ const (
 	Requested
 )
 
+const DumpFile = "/var/lib/go-dhcp/leases.json"
+
 type Lease struct {
-	TransactionId types.TxId
-	TTL           time.Time
-	State         LeaseState
-	ClientAddr    types.HwAddr
-	Address       types.Ipv4Addr
+	TransactionId types.TxId     `json:"TransactionID"`
+	TTL           time.Time      `json:"TTL"`
+	State         LeaseState     `json:"State"`
+	ClientAddr    types.HwAddr   `json:"ClientAddr"`
+	Address       types.Ipv4Addr `json:"Address"`
 }
 
 type ILeaseManager interface {
@@ -35,9 +40,51 @@ type LeaseManager struct {
 	count  byte
 }
 
+func (m LeaseManager) DumpLeases() {
+	err := os.MkdirAll(filepath.Dir(DumpFile), 0755)
+	if err != nil {
+		zap.S().Panic(err)
+	}
+
+	f, err := os.Create(DumpFile)
+	if err != nil {
+		zap.S().Panic(err)
+	}
+	defer f.Close()
+
+	leases := make([]Lease, len(m.leases))
+	for _, l := range m.leases {
+		leases = append(leases, l)
+	}
+
+	enc := json.NewEncoder(f)
+	enc.Encode(leases)
+	f.Sync()
+}
+
+func LoadLeases() (map[types.TxId]Lease, error) {
+	var leaseMap = make(map[types.TxId]Lease)
+
+	data, err := os.ReadFile(DumpFile)
+	if err != nil {
+		return leaseMap, err
+	}
+	var leases []Lease
+	json.Unmarshal(data, &leases)
+
+	for _, l := range leases {
+		leaseMap[l.TransactionId] = l
+	}
+	return leaseMap, nil
+}
+
 func NewLeaseManager() *LeaseManager {
+	leases, err := LoadLeases()
+	if err != nil {
+		zap.S().Warnf("Could not restore saved leases from %s: %s", DumpFile, err)
+	}
 	m := &LeaseManager{
-		leases: make(map[types.TxId]Lease),
+		leases: leases,
 	}
 	return m
 }
@@ -62,6 +109,9 @@ func (m *LeaseManager) Request(xid types.TxId, clientAddr types.HwAddr) (*Lease,
 	m.count += 1
 
 	zap.S().Debug("lease=", lease)
+
+	m.DumpLeases()
+
 	return &lease, nil
 }
 
@@ -71,6 +121,9 @@ func (m LeaseManager) Release(l Lease) error {
 		return fmt.Errorf("invalid lease %v", l)
 	}
 	delete(m.leases, l.TransactionId)
+
+	m.DumpLeases()
+
 	return nil
 }
 
diff --git a/pkg/types/json.go b/pkg/types/json.go
new file mode 100644
index 0000000..353ce21
--- /dev/null
+++ b/pkg/types/json.go
@@ -0,0 +1,46 @@
+package types
+
+import (
+	"fmt"
+	"net"
+	"strconv"
+
+	util "github.com/adrianokf/go-dhcp/pkg/util"
+)
+
+func (txid *TxId) UnmarshalText(text []byte) (err error) {
+	result, err := strconv.ParseUint(string(text), 16, 32)
+	if err != nil {
+		return err
+	}
+
+	copy(txid[:], util.U32ToByte(uint32(result)))
+	return nil
+}
+
+func (id TxId) MarshalText() ([]byte, error) {
+	return []byte(fmt.Sprintf("%x", id)), nil
+}
+
+func (addr *Ipv4Addr) UnmarshalText(text []byte) (err error) {
+	ip := net.ParseIP(string(text))
+	fmt.Println(ip)
+	if ip == nil {
+		return fmt.Errorf("could not parse IP address: '%s'", text)
+	}
+	*addr = Ipv4AddrFromNetIP(ip)
+	return nil
+}
+
+func (addr Ipv4Addr) MarshalText() ([]byte, error) {
+	return addr.ToNetIPv4().MarshalText()
+}
+
+func (addr HwAddr) MarshalText() ([]byte, error) {
+	return []byte(addr.String()), nil
+}
+
+func (addr *HwAddr) UnmarshalText(text []byte) (err error) {
+	*addr, err = HwAddrFromString(string(text))
+	return err
+}
diff --git a/pkg/types/types.go b/pkg/types/types.go
index 448da90..e72ccdd 100644
--- a/pkg/types/types.go
+++ b/pkg/types/types.go
@@ -1,5 +1,37 @@
 package types
 
+import (
+	"fmt"
+	"net"
+)
+
 type TxId [4]byte
 type Ipv4Addr [4]byte
 type HwAddr [16]byte
+
+const (
+	ServerPort = 67
+	ClientPort = 68
+)
+
+func Ipv4AddrFromNetIP(ip net.IP) Ipv4Addr {
+	ipv4 := ip.To4()
+	return Ipv4Addr{ipv4[0], ipv4[1], ipv4[2], ipv4[3]}
+}
+
+func (addr Ipv4Addr) ToNetIPv4() net.IP {
+	return net.IPv4(addr[0], addr[1], addr[2], addr[3])
+}
+
+func (addr Ipv4Addr) String() string {
+	return addr.ToNetIPv4().String()
+}
+
+func (addr HwAddr) String() string {
+	return fmt.Sprintf("%02x:%02x:%02x:%02x:%02x:%02x", addr[0], addr[1], addr[2], addr[3], addr[4], addr[5])
+}
+
+func HwAddrFromString(s string) (addr HwAddr, err error) {
+	_, err = fmt.Sscanf(s, "%02x:%02x:%02x:%02x:%02x:%02x", &addr[0], &addr[1], &addr[2], &addr[3], &addr[4], &addr[5])
+	return addr, err
+}
diff --git a/cmd/util.go b/pkg/util/util.go
similarity index 69%
rename from cmd/util.go
rename to pkg/util/util.go
index 88b731e..371d39d 100644
--- a/cmd/util.go
+++ b/pkg/util/util.go
@@ -1,10 +1,10 @@
-package cmd
+package util
 
 import (
 	"encoding/binary"
 )
 
-func u32tob(u uint32) []byte {
+func U32ToByte(u uint32) []byte {
 	buf := make([]byte, 4)
 	binary.BigEndian.PutUint32(buf, u)
 	return buf