diff --git a/main.go b/main.go
index 33c3bd6..03aeb99 100644
--- a/main.go
+++ b/main.go
@@ -329,7 +329,11 @@ func handleNewIncomeConnection(inServer proxy.Server, defaultClientForThis proxy
 				)
 
 			}
-			wrappedConn.Close()
+			//see #241
+			if !errors.Is(err, netLayer.ErrDoNotClose) {
+				wrappedConn.Close()
+
+			}
 			return
 		}
 
diff --git a/netLayer/netlayer.go b/netLayer/netlayer.go
index 8e7fc39..4c0fcbb 100644
--- a/netLayer/netlayer.go
+++ b/netLayer/netlayer.go
@@ -27,7 +27,8 @@ import (
 )
 
 var (
-	ErrTimeout = errors.New("timeout")
+	ErrTimeout    = errors.New("timeout")
+	ErrDoNotClose = errors.New("do not close")
 )
 
 // c.SetDeadline(time.Time{})
diff --git a/tlsLayer/shadow.go b/tlsLayer/shadow.go
index 556101a..9932305 100644
--- a/tlsLayer/shadow.go
+++ b/tlsLayer/shadow.go
@@ -98,7 +98,9 @@ func shadowTls2(servername string, clientConn net.Conn, password string) (result
 	}
 
 	hashW := utils.NewHashWriter(clientConn, []byte(password))
-	go io.Copy(hashW, fakeConn)
+
+	go io.Copy(hashW, fakeConn) //write real server response back to client
+
 	var firstPayload *bytes.Buffer
 	firstPayload, err = shadowCopyHandshakeClientToFake(fakeConn, clientConn, hashW)
 
@@ -123,8 +125,9 @@ func shadowTls2(servername string, clientConn net.Conn, password string) (result
 		}
 
 		hashW.StopHashing()
-		go io.Copy(fakeConn, clientConn)
-		return nil, errors.New("not real shadowTlsClient, fallback")
+		go io.Copy(fakeConn, clientConn) //write client request to real server
+
+		return nil, utils.ErrInErr{ErrDetail: netLayer.ErrDoNotClose, ErrDesc: "not real shadowTlsClient, fallback"}
 	}
 	return nil, err
 
diff --git a/utils/error.go b/utils/error.go
index 95c60e9..630fef8 100644
--- a/utils/error.go
+++ b/utils/error.go
@@ -165,7 +165,9 @@ func (e Errs) String() string {
 	for _, err := range e.List {
 		sb.WriteString(strconv.Itoa(err.Index))
 		sb.WriteString(", ")
-		sb.WriteString(err.E.Error())
+		if err.E != nil {
+			sb.WriteString(err.E.Error())
+		}
 		sb.WriteString("\n")
 
 	}
diff --git a/utils/io.go b/utils/io.go
index 7d4d133..589532a 100644
--- a/utils/io.go
+++ b/utils/io.go
@@ -42,6 +42,41 @@ func ClassicCopy(w io.Writer, r io.Reader) (written int64, err error) {
 	return
 }
 
+// 同ClassicCopy，但给出更详细的err
+func ClassicCopy_detailErr(w io.Writer, r io.Reader) (written int64, err error) {
+	bs := GetPacket()
+	defer PutPacket(bs)
+	for {
+
+		nr, er := r.Read(bs)
+		if nr > 0 {
+			nw, ew := w.Write(bs[0:nr])
+
+			if nw < 0 || nr < nw {
+				nw = 0
+				if ew == nil {
+					ew = ErrInvalidWrite
+				}
+			}
+			written += int64(nw)
+			if ew != nil {
+				err = ErrInErr{ErrDetail: Errs{[]ErrsItem{{Index: 1, E: ErrInErr{ErrDetail: ew, Data: []int{nr, nw}}}, {Index: 2, E: er}}}, ErrDesc: "ew"}
+				break
+			}
+			if nr != nw {
+				err = io.ErrShortWrite
+				break
+			}
+		}
+		if er != nil {
+
+			err = ErrInErr{ErrDetail: er, ErrDesc: "er"}
+			break
+		}
+	}
+	return
+}
+
 // 一种简单的读写组合, 在ws包中被用到.
 type RW struct {
 	io.Reader