diff --git a/.gitignore b/.gitignore
new file mode 100644
index 00000000..c765108d
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,5 @@
+*.swp
+*.swo
+*.bak
+.DS_Store
+vendor
diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 00000000..81e30fcc
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,57 @@
+# Changelog
+
+## 0.4.0 (March 6, 2017)
+
+BREAKING CHANGES: 
+
+- DialSeeds now takes an AddrBook and returns an error: `DialSeeds(*AddrBook, []string) error`
+- NewNetAddressString now returns an error: `NewNetAddressString(string) (*NetAddress, error)`
+
+FEATURES:
+
+- `NewNetAddressStrings([]string) ([]*NetAddress, error)`
+- `AddrBook.Save()`
+
+IMPROVEMENTS:
+
+- PexReactor responsible for starting and stopping the AddrBook
+
+BUG FIXES:
+
+- DialSeeds returns an error instead of panicking on bad addresses
+
+## 0.3.5 (January 12, 2017)
+
+FEATURES
+
+- Toggle strict routability in the AddrBook 
+
+BUG FIXES
+
+- Close filtered out connections
+- Fixes for MakeConnectedSwitches and Connect2Switches
+
+## 0.3.4 (August 10, 2016)
+
+FEATURES:
+
+- Optionally filter connections by address or public key
+
+## 0.3.3 (May 12, 2016)
+
+FEATURES:
+
+- FuzzConn
+
+## 0.3.2 (March 12, 2016)
+
+IMPROVEMENTS:
+
+- Memory optimizations
+
+## 0.3.1 ()
+
+FEATURES: 
+
+- Configurable parameters
+
diff --git a/addrbook.go b/addrbook.go
index 2bbae64f..ace0dba4 100644
--- a/addrbook.go
+++ b/addrbook.go
@@ -135,6 +135,9 @@ func (a *AddrBook) OnStart() error {
 
 func (a *AddrBook) OnStop() {
 	a.BaseService.OnStop()
+}
+
+func (a *AddrBook) Wait() {
 	a.wg.Wait()
 }
 
@@ -153,6 +156,7 @@ func (a *AddrBook) OurAddresses() []*NetAddress {
 	return addrs
 }
 
+// NOTE: addr must not be nil
 func (a *AddrBook) AddAddress(addr *NetAddress, src *NetAddress) {
 	a.mtx.Lock()
 	defer a.mtx.Unlock()
@@ -368,6 +372,12 @@ func (a *AddrBook) loadFromFile(filePath string) bool {
 	return true
 }
 
+// Save saves the book.
+func (a *AddrBook) Save() {
+	log.Info("Saving AddrBook to file", "size", a.Size())
+	a.saveToFile(a.filePath)
+}
+
 /* Private methods */
 
 func (a *AddrBook) saveRoutine() {
diff --git a/addrbook_test.go b/addrbook_test.go
index d5a83da8..7e8cb8d7 100644
--- a/addrbook_test.go
+++ b/addrbook_test.go
@@ -5,9 +5,9 @@ import (
 	"io/ioutil"
 	"math/rand"
 	"testing"
-)
 
-const addrBookStrict = true
+	"github.com/stretchr/testify/assert"
+)
 
 func createTempFileName(prefix string) string {
 	f, err := ioutil.TempFile("", prefix)
@@ -22,23 +22,117 @@ func createTempFileName(prefix string) string {
 	return fname
 }
 
-func TestEmpty(t *testing.T) {
+func TestAddrBookSaveLoad(t *testing.T) {
 	fname := createTempFileName("addrbook_test")
-	// t.Logf("New tempfile name: %v", fname)
 
-	// Save an empty book & load it
-	book := NewAddrBook(fname, addrBookStrict)
+	// 0 addresses
+	book := NewAddrBook(fname, true)
 	book.saveToFile(fname)
 
-	book = NewAddrBook(fname, addrBookStrict)
+	book = NewAddrBook(fname, true)
 	book.loadFromFile(fname)
 
-	if book.Size() != 0 {
-		t.Errorf("Expected 0 addresses, found %v", book.Size())
+	assert.Zero(t, book.Size())
+
+	// 100 addresses
+	randAddrs := randNetAddressPairs(t, 100)
+
+	for _, addrSrc := range randAddrs {
+		book.AddAddress(addrSrc.addr, addrSrc.src)
+	}
+
+	assert.Equal(t, 100, book.Size())
+	book.saveToFile(fname)
+
+	book = NewAddrBook(fname, true)
+	book.loadFromFile(fname)
+
+	assert.Equal(t, 100, book.Size())
+}
+
+func TestAddrBookLookup(t *testing.T) {
+	fname := createTempFileName("addrbook_test")
+
+	randAddrs := randNetAddressPairs(t, 100)
+
+	book := NewAddrBook(fname, true)
+	for _, addrSrc := range randAddrs {
+		addr := addrSrc.addr
+		src := addrSrc.src
+		book.AddAddress(addr, src)
+
+		ka := book.addrLookup[addr.String()]
+		assert.NotNil(t, ka, "Expected to find KnownAddress %v but wasn't there.", addr)
+
+		if !(ka.Addr.Equals(addr) && ka.Src.Equals(src)) {
+			t.Fatalf("KnownAddress doesn't match addr & src")
+		}
 	}
 }
 
-func randIPv4Address() *NetAddress {
+func TestAddrBookPromoteToOld(t *testing.T) {
+	fname := createTempFileName("addrbook_test")
+
+	randAddrs := randNetAddressPairs(t, 100)
+
+	book := NewAddrBook(fname, true)
+	for _, addrSrc := range randAddrs {
+		book.AddAddress(addrSrc.addr, addrSrc.src)
+	}
+
+	// Attempt all addresses.
+	for _, addrSrc := range randAddrs {
+		book.MarkAttempt(addrSrc.addr)
+	}
+
+	// Promote half of them
+	for i, addrSrc := range randAddrs {
+		if i%2 == 0 {
+			book.MarkGood(addrSrc.addr)
+		}
+	}
+
+	// TODO: do more testing :)
+
+	selection := book.GetSelection()
+	t.Logf("selection: %v", selection)
+
+	if len(selection) > book.Size() {
+		t.Errorf("selection could not be bigger than the book")
+	}
+}
+
+func TestAddrBookHandlesDuplicates(t *testing.T) {
+	fname := createTempFileName("addrbook_test")
+
+	book := NewAddrBook(fname, true)
+
+	randAddrs := randNetAddressPairs(t, 100)
+
+	differentSrc := randIPv4Address(t)
+	for _, addrSrc := range randAddrs {
+		book.AddAddress(addrSrc.addr, addrSrc.src)
+		book.AddAddress(addrSrc.addr, addrSrc.src)  // duplicate
+		book.AddAddress(addrSrc.addr, differentSrc) // different src
+	}
+
+	assert.Equal(t, 100, book.Size())
+}
+
+type netAddressPair struct {
+	addr *NetAddress
+	src  *NetAddress
+}
+
+func randNetAddressPairs(t *testing.T, n int) []netAddressPair {
+	randAddrs := make([]netAddressPair, n)
+	for i := 0; i < n; i++ {
+		randAddrs[i] = netAddressPair{addr: randIPv4Address(t), src: randIPv4Address(t)}
+	}
+	return randAddrs
+}
+
+func randIPv4Address(t *testing.T) *NetAddress {
 	for {
 		ip := fmt.Sprintf("%v.%v.%v.%v",
 			rand.Intn(254)+1,
@@ -47,117 +141,10 @@ func randIPv4Address() *NetAddress {
 			rand.Intn(255),
 		)
 		port := rand.Intn(65535-1) + 1
-		addr := NewNetAddressString(fmt.Sprintf("%v:%v", ip, port))
+		addr, err := NewNetAddressString(fmt.Sprintf("%v:%v", ip, port))
+		assert.Nil(t, err, "error generating rand network address")
 		if addr.Routable() {
 			return addr
 		}
 	}
 }
-
-func TestSaveAddresses(t *testing.T) {
-	fname := createTempFileName("addrbook_test")
-	//t.Logf("New tempfile name: %v", fname)
-
-	// Create some random addresses
-	randAddrs := []struct {
-		addr *NetAddress
-		src  *NetAddress
-	}{}
-	for i := 0; i < 100; i++ {
-		addr := randIPv4Address()
-		src := randIPv4Address()
-		randAddrs = append(randAddrs, struct {
-			addr *NetAddress
-			src  *NetAddress
-		}{
-			addr: addr,
-			src:  src,
-		})
-	}
-
-	// Create the book & populate & save
-	book := NewAddrBook(fname, addrBookStrict)
-	for _, addrSrc := range randAddrs {
-		book.AddAddress(addrSrc.addr, addrSrc.src)
-	}
-	if book.Size() != 100 {
-		t.Errorf("Expected 100 addresses, found %v", book.Size())
-	}
-	book.saveToFile(fname)
-
-	// Reload the book
-	book = NewAddrBook(fname, addrBookStrict)
-	book.loadFromFile(fname)
-
-	// Test ...
-
-	if book.Size() != 100 {
-		t.Errorf("Expected 100 addresses, found %v", book.Size())
-	}
-
-	for _, addrSrc := range randAddrs {
-		addr := addrSrc.addr
-		src := addrSrc.src
-		ka := book.addrLookup[addr.String()]
-		if ka == nil {
-			t.Fatalf("Expected to find KnownAddress %v but wasn't there.", addr)
-		}
-		if !(ka.Addr.Equals(addr) && ka.Src.Equals(src)) {
-			t.Fatalf("KnownAddress doesn't match addr & src")
-		}
-	}
-}
-
-func TestPromoteToOld(t *testing.T) {
-	fname := createTempFileName("addrbook_test")
-	t.Logf("New tempfile name: %v", fname)
-
-	// Create some random addresses
-	randAddrs := []struct {
-		addr *NetAddress
-		src  *NetAddress
-	}{}
-	for i := 0; i < 100; i++ {
-		addr := randIPv4Address()
-		src := randIPv4Address()
-		randAddrs = append(randAddrs, struct {
-			addr *NetAddress
-			src  *NetAddress
-		}{
-			addr: addr,
-			src:  src,
-		})
-	}
-
-	// Create the book & populate & save
-	book := NewAddrBook(fname, addrBookStrict)
-	for _, addrSrc := range randAddrs {
-		book.AddAddress(addrSrc.addr, addrSrc.src)
-	}
-	// Attempt all addresses.
-	for _, addrSrc := range randAddrs {
-		book.MarkAttempt(addrSrc.addr)
-	}
-	// Promote half of them
-	for i, addrSrc := range randAddrs {
-		if i%2 == 0 {
-			book.MarkGood(addrSrc.addr)
-		}
-	}
-	book.saveToFile(fname)
-
-	// Reload the book
-	book = NewAddrBook(fname, addrBookStrict)
-	book.loadFromFile(fname)
-
-	// Test ...
-
-	if book.Size() != 100 {
-		t.Errorf("Expected 100 addresses, found %v", book.Size())
-	}
-
-	// TODO: do more testing :)
-
-	selection := book.GetSelection()
-	t.Logf("selection: %v", selection)
-}
diff --git a/listener.go b/listener.go
index 1d7fb956..962c2b14 100644
--- a/listener.go
+++ b/listener.go
@@ -70,7 +70,11 @@ func NewDefaultListener(protocol string, lAddr string, skipUPNP bool) Listener {
 	log.Info("Local listener", "ip", listenerIP, "port", listenerPort)
 
 	// Determine internal address...
-	var intAddr *NetAddress = NewNetAddressString(lAddr)
+	var intAddr *NetAddress
+	intAddr, err = NewNetAddressString(lAddr)
+	if err != nil {
+		PanicCrisis(err)
+	}
 
 	// Determine external address...
 	var extAddr *NetAddress
diff --git a/netaddress.go b/netaddress.go
index 34dc5caf..90fcf6a4 100644
--- a/netaddress.go
+++ b/netaddress.go
@@ -5,11 +5,12 @@
 package p2p
 
 import (
+	"errors"
 	"net"
 	"strconv"
 	"time"
 
-	. "github.com/tendermint/go-common"
+	cmn "github.com/tendermint/go-common"
 )
 
 type NetAddress struct {
@@ -34,27 +35,43 @@ func NewNetAddress(addr net.Addr) *NetAddress {
 }
 
 // Also resolves the host if host is not an IP.
-func NewNetAddressString(addr string) *NetAddress {
+func NewNetAddressString(addr string) (*NetAddress, error) {
+
 	host, portStr, err := net.SplitHostPort(addr)
 	if err != nil {
-		PanicSanity(err)
+		return nil, err
 	}
+
 	ip := net.ParseIP(host)
 	if ip == nil {
 		if len(host) > 0 {
 			ips, err := net.LookupIP(host)
 			if err != nil {
-				PanicSanity(err)
+				return nil, err
 			}
 			ip = ips[0]
 		}
 	}
+
 	port, err := strconv.ParseUint(portStr, 10, 16)
 	if err != nil {
-		PanicSanity(err)
+		return nil, err
 	}
+
 	na := NewNetAddressIPPort(ip, uint16(port))
-	return na
+	return na, nil
+}
+
+func NewNetAddressStrings(addrs []string) ([]*NetAddress, error) {
+	netAddrs := make([]*NetAddress, len(addrs))
+	for i, addr := range addrs {
+		netAddr, err := NewNetAddressString(addr)
+		if err != nil {
+			return nil, errors.New(cmn.Fmt("Error in address %s: %v", addr, err))
+		}
+		netAddrs[i] = netAddr
+	}
+	return netAddrs, nil
 }
 
 func NewNetAddressIPPort(ip net.IP, port uint16) *NetAddress {
@@ -81,7 +98,7 @@ func (na *NetAddress) Less(other interface{}) bool {
 	if o, ok := other.(*NetAddress); ok {
 		return na.String() < o.String()
 	} else {
-		PanicSanity("Cannot compare unequal types")
+		cmn.PanicSanity("Cannot compare unequal types")
 		return false
 	}
 }
diff --git a/pex_reactor.go b/pex_reactor.go
index d7ccc761..45c4c96d 100644
--- a/pex_reactor.go
+++ b/pex_reactor.go
@@ -42,12 +42,14 @@ func NewPEXReactor(book *AddrBook) *PEXReactor {
 
 func (pexR *PEXReactor) OnStart() error {
 	pexR.BaseReactor.OnStart()
+	pexR.book.Start()
 	go pexR.ensurePeersRoutine()
 	return nil
 }
 
 func (pexR *PEXReactor) OnStop() {
 	pexR.BaseReactor.OnStop()
+	pexR.book.Stop()
 }
 
 // Implements Reactor
@@ -64,7 +66,13 @@ func (pexR *PEXReactor) GetChannels() []*ChannelDescriptor {
 // Implements Reactor
 func (pexR *PEXReactor) AddPeer(peer *Peer) {
 	// Add the peer to the address book
-	netAddr := NewNetAddressString(peer.ListenAddr)
+	netAddr, err := NewNetAddressString(peer.ListenAddr)
+	if err != nil {
+		// this should never happen
+		log.Error("Error in AddPeer: invalid peer address", "addr", peer.ListenAddr, "error", err)
+		return
+	}
+
 	if peer.IsOutbound() {
 		if pexR.book.NeedMoreAddrs() {
 			pexR.RequestPEX(peer)
@@ -104,12 +112,13 @@ func (pexR *PEXReactor) Receive(chID byte, src *Peer, msgBytes []byte) {
 		// (We don't want to get spammed with bad peers)
 		srcAddr := src.Connection().RemoteAddress
 		for _, addr := range msg.Addrs {
-			pexR.book.AddAddress(addr, srcAddr)
+			if addr != nil {
+				pexR.book.AddAddress(addr, srcAddr)
+			}
 		}
 	default:
 		log.Warn(Fmt("Unknown message type %v", reflect.TypeOf(msg)))
 	}
-
 }
 
 // Asks peer for more addresses.
diff --git a/switch.go b/switch.go
index 841c44f8..eed8ceea 100644
--- a/switch.go
+++ b/switch.go
@@ -296,20 +296,38 @@ func (sw *Switch) startInitPeer(peer *Peer) {
 	sw.addPeerToReactors(peer) // run AddPeer on each reactor
 }
 
-// Dial a list of seeds in random order
-// Spawns a go routine for each dial
-func (sw *Switch) DialSeeds(seeds []string) {
+// Dial a list of seeds asynchronously in random order
+func (sw *Switch) DialSeeds(addrBook *AddrBook, seeds []string) error {
+
+	netAddrs, err := NewNetAddressStrings(seeds)
+	if err != nil {
+		return err
+	}
+
+	if addrBook != nil {
+		// add seeds to `addrBook`
+		ourAddrS := sw.nodeInfo.ListenAddr
+		ourAddr, _ := NewNetAddressString(ourAddrS)
+		for _, netAddr := range netAddrs {
+			// do not add ourselves
+			if netAddr.Equals(ourAddr) {
+				continue
+			}
+			addrBook.AddAddress(netAddr, ourAddr)
+		}
+		addrBook.Save()
+	}
+
 	// permute the list, dial them in random order.
-	perm := rand.Perm(len(seeds))
+	perm := rand.Perm(len(netAddrs))
 	for i := 0; i < len(perm); i++ {
 		go func(i int) {
 			time.Sleep(time.Duration(rand.Int63n(3000)) * time.Millisecond)
 			j := perm[i]
-			addr := NewNetAddressString(seeds[j])
-
-			sw.dialSeed(addr)
+			sw.dialSeed(netAddrs[j])
 		}(i)
 	}
+	return nil
 }
 
 func (sw *Switch) dialSeed(addr *NetAddress) {
diff --git a/version.go b/version.go
index af98bef3..c13ec447 100644
--- a/version.go
+++ b/version.go
@@ -1,3 +1,3 @@
 package p2p
 
-const Version = "0.3.5" // minor fixes
+const Version = "0.4.0" // DialSeeds returns an error