Revert "improve transport performance with bufio (#321)" (#323)

This reverts commit 8e52e49.

clients.go

@@ -584,25 +584,12 @@ func (cl *Client) WritePacket(pk packets.Packet) error {
 		return packets.ErrPacketTooLarge // [MQTT-3.1.2-24] [MQTT-3.1.2-25]
 	}
 
+	nb := net.Buffers{buf.Bytes()}
 	n, err := func() (int64, error) {
 		cl.Lock()
 		defer cl.Unlock()
-
-		length, err := cl.Net.bconn.Write(buf.Bytes())
-		if nil != err {
-			return 0, err
-		}
-
-		// immediate flush if no packets in channel and write buffer is not empty
-		if len(cl.State.outbound) == 0 && cl.Net.bconn.Writer.Buffered() > 0 {
-			if err = cl.Net.bconn.Flush(); nil != err {
-				return 0, err
-			}
-		}
-
-		return int64(length), nil
+		return nb.WriteTo(cl.Net.Conn)
 	}()
-
 	if err != nil {
 		return err
 	}

server_test.go

@@ -15,7 +15,6 @@ import (
 	"sync/atomic"
 	"testing"
 	"time"
-	"bufio"
 
 	"github.com/mochi-mqtt/server/v2/hooks/storage"
 	"github.com/mochi-mqtt/server/v2/listeners"
@@ -2469,10 +2468,6 @@ func TestServerProcessInboundQos2Flow(t *testing.T) {
 		t.Run("qos step"+strconv.Itoa(i), func(t *testing.T) {
 			r, w = net.Pipe()
 			cl.Net.Conn = w
-			cl.Net.bconn = bufio.NewReadWriter(
-				bufio.NewReaderSize(w, cl.ops.options.ClientNetReadBufferSize),
-				bufio.NewWriterSize(w, cl.ops.options.ClientNetWriteBufferSize),
-			)
 
 			recv := make(chan []byte)
 			go func() { // receive the ack
@@ -2548,10 +2543,6 @@ func TestServerProcessOutboundQos2Flow(t *testing.T) {
 			r, w := net.Pipe()
 			time.Sleep(time.Millisecond)
 			cl.Net.Conn = w
-			cl.Net.bconn = bufio.NewReadWriter(
-				bufio.NewReaderSize(w, cl.ops.options.ClientNetReadBufferSize),
-				bufio.NewWriterSize(w, cl.ops.options.ClientNetWriteBufferSize),
-			)
 
 			recv := make(chan []byte)
 			go func() { // receive the ack