diff --git a/common/dialer/default.go b/common/dialer/default.go
index c9f1df89..4cf13883 100644
--- a/common/dialer/default.go
+++ b/common/dialer/default.go
@@ -9,6 +9,7 @@ import (
 	"github.com/sagernet/sing-box/adapter"
 	C "github.com/sagernet/sing-box/constant"
 	"github.com/sagernet/sing-box/option"
+	"github.com/sagernet/sing/common"
 	"github.com/sagernet/sing/common/control"
 	M "github.com/sagernet/sing/common/metadata"
 
@@ -69,7 +70,15 @@ func NewDefault(router adapter.Router, options option.DialerOptions) *DefaultDia
 }
 
 func (d *DefaultDialer) DialContext(ctx context.Context, network string, address M.Socksaddr) (net.Conn, error) {
-	return d.Dialer.DialContext(ctx, network, address.Unwrap().String())
+	conn, err := d.Dialer.DialContext(ctx, network, address.Unwrap().String())
+	if err != nil {
+		return nil, err
+	}
+	if tcpConn, isTCP := common.Cast[*net.TCPConn](conn); isTCP {
+		tcpConn.SetKeepAlive(true)
+		tcpConn.SetKeepAlivePeriod(C.DefaultTCPKeepAlivePeriod)
+	}
+	return conn, nil
 }
 
 func (d *DefaultDialer) ListenPacket(ctx context.Context, destination M.Socksaddr) (net.PacketConn, error) {
diff --git a/constant/timeout.go b/constant/timeout.go
index 26037dfa..57cced2c 100644
--- a/constant/timeout.go
+++ b/constant/timeout.go
@@ -3,8 +3,9 @@ package constant
 import "time"
 
 const (
-	DefaultTCPTimeout      = 5 * time.Second
-	ReadPayloadTimeout     = 300 * time.Millisecond
-	URLTestTimeout         = DefaultTCPTimeout
-	DefaultURLTestInterval = 1 * time.Minute
+	DefaultTCPTimeout         = 5 * time.Second
+	DefaultTCPKeepAlivePeriod = 20 * time.Second
+	ReadPayloadTimeout        = 300 * time.Millisecond
+	URLTestTimeout            = DefaultTCPTimeout
+	DefaultURLTestInterval    = 1 * time.Minute
 )