diff --git a/cmd/ping/main.go b/cmd/ping/main.go
index ad0a891..1ac429c 100644
--- a/cmd/ping/main.go
+++ b/cmd/ping/main.go
@@ -93,6 +93,7 @@ func main() {
 	}
 
 	req := ping.Request{
+		ID:   os.Getpid(),
 		Dst:  net.ParseIP(host.String()),
 		Src:  net.ParseIP(getAddr(*iface)),
 		Data: data,
diff --git a/ping.go b/ping.go
index 5da9bd5..bec7fa5 100644
--- a/ping.go
+++ b/ping.go
@@ -50,10 +50,19 @@ type Response struct {
 }
 
 // Client is a ping client.
-type Client struct{}
+type Client struct {
+	// CheckResponse checks whether the response is valid.
+	CheckResponse func(*Response) bool
+}
 
 // DefaultClient is the default client used by Do.
-var DefaultClient = &Client{}
+var DefaultClient = &Client{CheckResponse: CheckResponse}
+
+// CheckResponse checks whether the id and the seq are equal respectively
+// between request and response.
+func CheckResponse(resp *Response) bool {
+	return resp.ID == resp.Req.ID && int(resp.Seq) == resp.Req.Seq
+}
 
 // NewRequest resolves dst as an IPv4 address and returns a pointer to a request
 // using that as the destination.
@@ -108,28 +117,18 @@ func (c *Client) Do(ctx context.Context, req *Request) (*Response, error) {
 		}
 	}
 
-	var (
-		resp    *Response
-		readErr error
-	)
-
 	sentAt, err := send(ctx, conn, req)
 	if err != nil {
 		return nil, err
 	}
 
-	resp, readErr = read(ctx, conn)
-	if readErr != nil {
-		return nil, readErr
+	resp, err := read(ctx, conn, req, c.CheckResponse)
+	if err != nil {
+		return nil, err
 	}
 
 	resp.RTT = resp.rcvdAt.Sub(sentAt)
 	req.sentAt = sentAt
-	resp.Req = req
-
-	if readErr != nil {
-		return nil, readErr
-	}
 
 	return resp, nil
 }
@@ -199,18 +198,20 @@ func (req *Request) proto() int {
 	return protocolIPv4ICMP
 }
 
-func read(ctx context.Context, conn *icmp.PacketConn) (*Response, error) {
+func read(ctx context.Context, conn *icmp.PacketConn, req *Request,
+	check func(*Response) bool) (*Response, error) {
 	if c4 := conn.IPv4PacketConn(); c4 != nil {
-		return read4(ctx, c4)
+		return read4(ctx, c4, req, check)
 	}
 	c6 := conn.IPv6PacketConn()
 	if c6 == nil {
 		return nil, errors.New("bad icmp connection type")
 	}
-	return read6(ctx, c6)
+	return read6(ctx, c6, req, check)
 }
 
-func read4(ctx context.Context, conn *ipv4.PacketConn) (*Response, error) {
+func read4(ctx context.Context, conn *ipv4.PacketConn, req *Request,
+	check func(*Response) bool) (*Response, error) {
 	for {
 		select {
 		case <-ctx.Done():
@@ -259,9 +260,18 @@ func read4(ctx context.Context, conn *ipv4.PacketConn) (*Response, error) {
 				ttl = cm.TTL
 			}
 
-			srcHost, _, _ := net.SplitHostPort(src.String())
-			dstHost, _, _ := net.SplitHostPort(conn.LocalAddr().String())
-			return &Response{
+			srcHost, _, err := net.SplitHostPort(src.String())
+			if err != nil {
+				srcHost = src.String()
+			}
+
+			dstHost, _, err := net.SplitHostPort(conn.LocalAddr().String())
+			if err != nil {
+				dstHost = conn.LocalAddr().String()
+			}
+
+			resp := &Response{
+				Req:         req,
 				ID:          id,
 				Seq:         seq,
 				Data:        bytesReceived[:n],
@@ -270,12 +280,16 @@ func read4(ctx context.Context, conn *ipv4.PacketConn) (*Response, error) {
 				Dst:         net.ParseIP(dstHost),
 				TTL:         ttl,
 				rcvdAt:      rcv,
-			}, nil
+			}
+			if check == nil || check(resp) {
+				return resp, nil
+			}
 		}
 	}
 }
 
-func read6(ctx context.Context, conn *ipv6.PacketConn) (*Response, error) {
+func read6(ctx context.Context, conn *ipv6.PacketConn, req *Request,
+	check func(*Response) bool) (*Response, error) {
 	for {
 		select {
 		case <-ctx.Done():
@@ -324,9 +338,18 @@ func read6(ctx context.Context, conn *ipv6.PacketConn) (*Response, error) {
 				ttl = cm.HopLimit
 			}
 
-			srcHost, _, _ := net.SplitHostPort(src.String())
-			dstHost, _, _ := net.SplitHostPort(conn.LocalAddr().String())
-			return &Response{
+			srcHost, _, err := net.SplitHostPort(src.String())
+			if err != nil {
+				srcHost = src.String()
+			}
+
+			dstHost, _, err := net.SplitHostPort(conn.LocalAddr().String())
+			if err != nil {
+				dstHost = conn.LocalAddr().String()
+			}
+
+			resp := &Response{
+				Req:         req,
 				ID:          id,
 				Seq:         seq,
 				Data:        bytesReceived[:n],
@@ -335,7 +358,10 @@ func read6(ctx context.Context, conn *ipv6.PacketConn) (*Response, error) {
 				Dst:         net.ParseIP(dstHost),
 				TTL:         ttl,
 				rcvdAt:      rcv,
-			}, nil
+			}
+			if check == nil || check(resp) {
+				return resp, nil
+			}
 		}
 	}
 }
diff --git a/ping_test.go b/ping_test.go
index f589eaf..f06c7b4 100644
--- a/ping_test.go
+++ b/ping_test.go
@@ -12,6 +12,42 @@ import (
 	"github.com/glinton/ping"
 )
 
+func TestClient(t *testing.T) {
+	req1, err := ping.NewRequest("www.baidu.com")
+	if err != nil {
+		t.Error(err)
+		return
+	}
+	req1.ID = 101
+	req1.Seq = 201
+
+	req2 := *req1
+	req2.ID = 102
+	req2.Seq = 202
+
+	req3 := *req1
+	req3.ID = 103
+	req3.Seq = 203
+
+	wg := new(sync.WaitGroup)
+	wg.Add(3)
+	go testClient(t, wg, req1)
+	go testClient(t, wg, &req2)
+	go testClient(t, wg, &req3)
+	wg.Wait()
+}
+
+func testClient(t *testing.T, wg *sync.WaitGroup, req *ping.Request) {
+	defer wg.Done()
+
+	resp, err := ping.Do(context.Background(), req)
+	if err != nil {
+		t.Error(err)
+	} else if resp.ID != req.ID || int(resp.Seq) != req.Seq {
+		t.Error(req, resp)
+	}
+}
+
 func TestE2E(t *testing.T) {
 	c := &ping.Client{}