diff --git a/ipam/http_test.go b/ipam/http_test.go
index a42bf5ba..b8c972f0 100644
--- a/ipam/http_test.go
+++ b/ipam/http_test.go
@@ -4,7 +4,7 @@ import (
 	"fmt"
 	"io"
 	"io/ioutil"
-	"math/rand"
+	"net"
 	"net/http"
 	"strings"
 	"testing"
@@ -30,20 +30,25 @@ func doHTTP(method string, url string) (resp *http.Response, err error) {
 	return http.DefaultClient.Do(req)
 }
 
-func listenHTTP(port int, alloc *Allocator) {
+func listenHTTP(alloc *Allocator) int {
 	router := mux.NewRouter()
 	router.HandleFunc("/status", func(w http.ResponseWriter, r *http.Request) {
 		io.WriteString(w, fmt.Sprintln(alloc))
 	})
 	alloc.HandleHTTP(router)
 
-	srv := &http.Server{
-		Addr:    fmt.Sprintf(":%d", port),
-		Handler: router,
-	}
-	if err := srv.ListenAndServe(); err != nil {
+	httpListener, err := net.Listen("tcp", ":0")
+	if err != nil {
 		common.Error.Fatal("Unable to create http listener: ", err)
 	}
+
+	go func() {
+		srv := &http.Server{Handler: router}
+		if err := srv.Serve(httpListener); err != nil {
+			common.Error.Fatal("Unable to serve http: ", err)
+		}
+	}()
+	return httpListener.Addr().(*net.TCPAddr).Port
 }
 
 func allocURL(port int, containerID string) string {
@@ -61,11 +66,7 @@ func TestHttp(t *testing.T) {
 	)
 
 	alloc := makeAllocatorWithMockGossip(t, "08:00:27:01:c3:9a", testCIDR1, 1)
-	port := rand.Intn(10000) + 32768
-	fmt.Println("Http test on port", port)
-	go listenHTTP(port, alloc)
-
-	time.Sleep(100 * time.Millisecond) // Allow for http server to get going
+	port := listenHTTP(alloc)
 
 	alloc.claimRingForTesting()
 	// Ask the http server for a new address
@@ -98,9 +99,7 @@ func TestBadHttp(t *testing.T) {
 
 	alloc := makeAllocatorWithMockGossip(t, "08:00:27:01:c3:9a", testCIDR1, 1)
 	defer alloc.Stop()
-	port := rand.Intn(10000) + 32768
-	fmt.Println("BadHttp test on port", port)
-	go listenHTTP(port, alloc)
+	port := listenHTTP(alloc)
 
 	alloc.claimRingForTesting()
 	cidr1 := HTTPPost(t, allocURL(port, containerID))
@@ -136,11 +135,7 @@ func impTestHTTPCancel(t *testing.T) {
 	alloc := makeAllocatorWithMockGossip(t, "08:00:27:01:c3:9a", testCIDR1, 1)
 	defer alloc.Stop()
 	alloc.claimRingForTesting()
-	port := rand.Intn(10000) + 32768
-	fmt.Println("Http test on port", port)
-	go listenHTTP(port, alloc)
-
-	time.Sleep(100 * time.Millisecond) // Allow for http server to get going
+	port := listenHTTP(alloc)
 
 	// Stop the alloc so nothing actually works
 	unpause := alloc.pause()
diff --git a/nameserver/http.go b/nameserver/http.go
index 1f9a1e2b..64c0394a 100644
--- a/nameserver/http.go
+++ b/nameserver/http.go
@@ -17,7 +17,7 @@ func httpErrorAndLog(level *log.Logger, w http.ResponseWriter, msg string,
 	level.Printf("[http] "+logmsg, logargs...)
 }
 
-func ListenHTTP(version string, server *DNSServer, domain string, db Zone, port int) {
+func ServeHTTP(listener net.Listener, version string, server *DNSServer, domain string, db Zone) {
 
 	muxRouter := mux.NewRouter()
 
@@ -90,8 +90,7 @@ func ListenHTTP(version string, server *DNSServer, domain string, db Zone, port
 
 	http.Handle("/", muxRouter)
 
-	address := fmt.Sprintf(":%d", port)
-	if err := http.ListenAndServe(address, nil); err != nil {
-		Error.Fatal("[http] Unable to create http listener: ", err)
+	if err := http.Serve(listener, nil); err != nil {
+		Error.Fatal("[http] Unable to serve http: ", err)
 	}
 }
diff --git a/nameserver/http_test.go b/nameserver/http_test.go
index b0175fe7..44e5bfc0 100644
--- a/nameserver/http_test.go
+++ b/nameserver/http_test.go
@@ -2,13 +2,11 @@ package nameserver
 
 import (
 	"fmt"
-	"math/rand"
 	"net"
 	"net/http"
 	"net/url"
 	"strings"
 	"testing"
-	"time"
 
 	wt "github.com/weaveworks/weave/testing"
 )
@@ -35,11 +33,13 @@ func TestHttp(t *testing.T) {
 	wt.AssertNoErr(t, err)
 	defer zone.Stop()
 
-	port := rand.Intn(10000) + 32768
-	fmt.Println("Http test on port", port)
-	go ListenHTTP("", nil, testDomain, zone, port)
+	httpListener, err := net.Listen("tcp", ":0")
+	if err != nil {
+		t.Fatal("Unable to create http listener: ", err)
+	}
 
-	time.Sleep(100 * time.Millisecond) // Allow for http server to get going
+	port := httpListener.Addr().(*net.TCPAddr).Port
+	go ServeHTTP(httpListener, "", nil, testDomain, zone)
 
 	// Ask the http server to add our test address into the database
 	addrParts := strings.Split(testAddr1, "/")
diff --git a/weavedns/main.go b/weavedns/main.go
index bf0a89e3..0fc48523 100644
--- a/weavedns/main.go
+++ b/weavedns/main.go
@@ -127,8 +127,13 @@ func main() {
 		Error.Fatal("[main] Failed to initialize the WeaveDNS server", err)
 	}
 
+	httpListener, err := net.Listen("tcp", fmt.Sprintf(":%d", httpPort))
+	if err != nil {
+		Error.Fatal("[main] Unable to create http listener: ", err)
+	}
+
 	go SignalHandlerLoop(srv)
-	go weavedns.ListenHTTP(version, srv, domain, zone, httpPort)
+	go weavedns.ServeHTTP(httpListener, version, srv, domain, zone)
 
 	err = srv.Start()
 	if err != nil {