client_test.go             |  7 +++++--
 t.go                       |  2 +-
 tracker/udp/udp_test.go    |  6 ++++--
 tracker/udp/udp_unix.go    | 14 ++++++++++++++
 tracker/udp/udp_windows.go | 11 +++++++++++

diff --git a/client_test.go b/client_test.go
index 1000c3b03ae289f6824ccdaa9aabfb0b93eff3e7..22281efd6cde9bf0eaa6a0b03d7f48150ee5a500 100644
--- a/client_test.go
+++ b/client_test.go
@@ -788,13 +788,16 @@ 	)
 }
 
 func TestClientAddressInUse(t *testing.T) {
-	s, _ := NewUtpSocket("udp", ":50007", nil, log.Default)
+	s, _ := NewUtpSocket("udp", "localhost:50007", nil, log.Default)
 	if s != nil {
 		defer s.Close()
 	}
-	cfg := TestingConfig(t).SetListenAddr(":50007")
+	cfg := TestingConfig(t).SetListenAddr("localhost:50007")
 	cfg.DisableUTP = false
 	cl, err := NewClient(cfg)
+	if err == nil {
+		assert.Nil(t, cl.Close())
+	}
 	require.Error(t, err)
 	require.Nil(t, cl)
 }
diff --git a/t.go b/t.go
index af4fdec7f3c000cc6ab2fd36cb5204ac891c403a..45856cc7acbeaa5988074f74435d078a49111a57 100644
--- a/t.go
+++ b/t.go
@@ -235,8 +235,8 @@ }
 
 func (t *Torrent) AddPeers(pp []PeerInfo) (n int) {
 	t.cl.lock()
+	defer t.cl.unlock()
 	n = t.addPeers(pp)
-	t.cl.unlock()
 	return
 }
 
diff --git a/tracker/udp/udp_test.go b/tracker/udp/udp_test.go
index 51f58e4c2c1cfa533d49be9d963408d91f17194e..64aeb80ff7426c514f5f63e7c2eab71fb1b5851b 100644
--- a/tracker/udp/udp_test.go
+++ b/tracker/udp/udp_test.go
@@ -57,8 +57,10 @@ 	defer c.Close()
 	for msgLen := 1; ; msgLen *= 2 {
 		n, err := c.Write(make([]byte, msgLen))
 		if err != nil {
-			require.Contains(t, err.Error(), "message too long")
-			return
+			if isErrMessageTooLong(err) {
+				return
+			}
+			t.Fatalf("expected message too long error: %v", err)
 		}
 		if n < msgLen {
 			t.FailNow()
diff --git a/tracker/udp/udp_unix.go b/tracker/udp/udp_unix.go
new file mode 100644
index 0000000000000000000000000000000000000000..6fcf9ed18ec7c73d234de7ff7b6720b7a043c37d
--- /dev/null
+++ b/tracker/udp/udp_unix.go
@@ -0,0 +1,14 @@
+//go:build !windows
+
+package udp
+
+import (
+	"strings"
+)
+
+func isErrMessageTooLong(err error) bool {
+	if err == nil {
+		return false
+	}
+	return strings.Contains(err.Error(), "message too long")
+}
diff --git a/tracker/udp/udp_windows.go b/tracker/udp/udp_windows.go
new file mode 100644
index 0000000000000000000000000000000000000000..a289e9ec500e20db362c2ceae4bfa38643c299f2
--- /dev/null
+++ b/tracker/udp/udp_windows.go
@@ -0,0 +1,11 @@
+package udp
+
+import (
+	"errors"
+
+	"golang.org/x/sys/windows"
+)
+
+func isErrMessageTooLong(err error) bool {
+	return errors.Is(err, windows.WSAEMSGSIZE)
+}