diff --git a/.gitignore b/.gitignore
index 2ed562a..a62d708 100755
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,4 @@
 *.exe
 *~
 *bak
+*.swp
diff --git a/README.md b/README.md
index aa5f47e..21329bf 100755
--- a/README.md
+++ b/README.md
@@ -1,20 +1,21 @@
 socks-go
 =======
 
-A socks server implement by golang, support socks4/4a, socks5.
+A socks server implemented by golang, support socks4/4a, socks5.
 
+Only support connect command now.
 
 usage
 ====
 Usage example:
 
-    import "github.com/fangdingjun/socks"
+    import socks "github.com/fangdingjun/socks-go"
 
-    fucn main(){
+    func main(){
         l, _ := net.Listen("tcp", ":1080")
         for {
             conn, _ := l.Accept()
-            s := socks.SocksConn{conn}
-            go s.Serve()
+            s := socks.SocksConn{ClientConn: conn, Dial: nil} // Dial is a function which dial to the upstream server
+            go s.Serve() // serve the socks request
         }
     }
diff --git a/examples/server/.gitignore b/examples/server/.gitignore
new file mode 100644
index 0000000..254defd
--- /dev/null
+++ b/examples/server/.gitignore
@@ -0,0 +1 @@
+server
diff --git a/cmd/server/README.md b/examples/server/README.md
similarity index 100%
rename from cmd/server/README.md
rename to examples/server/README.md
diff --git a/cmd/server/server.go b/examples/server/server.go
old mode 100755
new mode 100644
similarity index 66%
rename from cmd/server/server.go
rename to examples/server/server.go
index 249ec7f..527f3c8
--- a/cmd/server/server.go
+++ b/examples/server/server.go
@@ -1,9 +1,10 @@
 package main
 
 import (
-	"github.com/fangdingjun/socks"
+	socks "github.com/fangdingjun/socks-go"
 	"log"
 	"net"
+	"time"
 )
 
 func main() {
@@ -18,7 +19,8 @@ func main() {
 			continue
 		}
 		log.Printf("connected from %s", c.RemoteAddr())
-		s := socks.SocksConn{ClientConn: c}
+		d := net.Dialer{Timeout: 10 * time.Second}
+		s := socks.SocksConn{ClientConn: c, Dial: d.Dial}
 		go s.Serve()
 	}
 }
diff --git a/socks.go b/socks.go
old mode 100755
new mode 100644
index 4c58e97..e150545
--- a/socks.go
+++ b/socks.go
@@ -4,6 +4,7 @@ import (
 	"io"
 	"log"
 	"net"
+	"time"
 )
 
 const (
@@ -15,25 +16,36 @@ const (
 	addrTypeIPv6   = 0x04
 )
 
+type dialFunc func(network, addr string) (net.Conn, error)
+
+// SocksConn present a client connection
 type SocksConn struct {
 	ClientConn net.Conn
+	Dial       dialFunc
 }
 
+// Serve serve the client
 func (s *SocksConn) Serve() {
 	buf := make([]byte, 1)
 
 	// read version
 	io.ReadFull(s.ClientConn, buf)
 
+	dial := s.Dial
+	if s.Dial == nil {
+		d := net.Dialer{Timeout: 10 * time.Second}
+		dial = d.Dial
+	}
+
 	switch buf[0] {
 	case socks4Version:
-		s4 := socks4Conn{client_conn: s.ClientConn}
+		s4 := socks4Conn{clientConn: s.ClientConn, dial: dial}
 		s4.Serve()
 	case socks5Version:
-		s5 := socks5Conn{client_conn: s.ClientConn}
+		s5 := socks5Conn{clientConn: s.ClientConn, dial: dial}
 		s5.Serve()
 	default:
-		log.Printf("error version %s", buf[0])
+		log.Printf("error version %d", buf[0])
 		s.ClientConn.Close()
 	}
 }
diff --git a/socks4.go b/socks4.go
index aa4cdc4..0eeda0d 100755
--- a/socks4.go
+++ b/socks4.go
@@ -8,13 +8,38 @@ import (
 	"net"
 )
 
+/*
+socks4 protocol
+
+request
+byte | 0  | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | ...  |
+     |0x04|cmd| port  |     ip        |  user\0  |
+
+reply
+byte | 0  |  1   | 2 | 3 | 4 | 5 | 6 | 7|
+     |0x00|status|       |              |
+
+
+socks4a protocol
+
+request
+byte | 0  | 1 | 2 | 3 |4 | 5 | 6 | 7 | 8 | ... |...     |
+     |0x04|cmd| port  |  0.0.0.x     |  user\0 |domain\0|
+
+reply
+byte | 0  |  1  | 2 | 3 | 4 | 5 | 6| 7 |
+	 |0x00|staus| port  |    ip        |
+
+*/
 type socks4Conn struct {
-	server_conn net.Conn
-	client_conn net.Conn
+	serverConn net.Conn
+	clientConn net.Conn
+	dial       dialFunc
 }
 
 func (s4 *socks4Conn) Serve() {
 	defer s4.Close()
+
 	if err := s4.processRequest(); err != nil {
 		log.Println(err)
 		return
@@ -22,20 +47,30 @@ func (s4 *socks4Conn) Serve() {
 }
 
 func (s4 *socks4Conn) Close() {
-	if s4.client_conn != nil {
-		s4.client_conn.Close()
+	if s4.clientConn != nil {
+		s4.clientConn.Close()
 	}
-	if s4.server_conn != nil {
-		s4.server_conn.Close()
+
+	if s4.serverConn != nil {
+		s4.serverConn.Close()
 	}
 }
 
 func (s4 *socks4Conn) forward() {
+
+	c := make(chan int, 2)
+
 	go func() {
-		io.Copy(s4.client_conn, s4.server_conn)
+		io.Copy(s4.clientConn, s4.serverConn)
+		c <- 1
 	}()
 
-	io.Copy(s4.server_conn, s4.client_conn)
+	go func() {
+		io.Copy(s4.serverConn, s4.clientConn)
+		c <- 1
+	}()
+
+	<-c
 }
 
 func (s4 *socks4Conn) processRequest() error {
@@ -43,18 +78,22 @@ func (s4 *socks4Conn) processRequest() error {
 	// process command and target here
 
 	buf := make([]byte, 128)
-	n, err := io.ReadAtLeast(s4.client_conn, buf, 8)
+
+	// read header
+	n, err := io.ReadAtLeast(s4.clientConn, buf, 8)
 	if err != nil {
 		return err
 	}
 
-	// only support connect
+	// command only support connect
 	if buf[0] != cmdConnect {
 		return fmt.Errorf("error command %s", buf[0])
 	}
 
+	// get port
 	port := binary.BigEndian.Uint16(buf[1:3])
 
+	// get ip
 	ip := net.IP(buf[3:7])
 
 	// NULL-terminated user string
@@ -87,12 +126,12 @@ func (s4 *socks4Conn) processRequest() error {
 
 	// reply user with connect success
 	// if dial to target failed, user will receive connection reset
-	s4.client_conn.Write([]byte{0x00, 0x5a, 0x01, 0x02, 0x00, 0x00, 0x00, 0x00})
+	s4.clientConn.Write([]byte{0x00, 0x5a, 0x01, 0x02, 0x00, 0x00, 0x00, 0x00})
 
-	log.Printf("connecting to %s", target)
+	//log.Printf("connecting to %s\r\n", target)
 
 	// connect to the target
-	s4.server_conn, err = net.Dial("tcp", target)
+	s4.serverConn, err = s4.dial("tcp", target)
 	if err != nil {
 		return err
 	}
diff --git a/socks5.go b/socks5.go
old mode 100755
new mode 100644
index dd2a8f1..d624a4d
--- a/socks5.go
+++ b/socks5.go
@@ -9,14 +9,41 @@ import (
 	"encoding/binary"
 )
 
+/*
+socks5 protocol
+
+initial
+
+byte | 0  |   1    | 2 | ...... | n |
+     |0x05|num auth|  auth methods  |
+
+
+reply
+
+byte | 0  |  1  |
+     |0x05| auth|
+
+
+request
+
+byte | 0  | 1 | 2  |   3    | 4 | .. | n-2 | n-1| n |
+     |0x05|cmd|0x00|addrtype|      addr    |  port  |
+
+response
+byte |0   |  1   | 2  |   3    | 4 | .. | n-2 | n-1 | n |
+     |0x05|status|0x00|addrtype|     addr     |  port   |
+
+*/
 type socks5Conn struct {
 	//addr        string
-	client_conn net.Conn
-	server_conn net.Conn
+	clientConn net.Conn
+	serverConn net.Conn
+	dial       dialFunc
 }
 
 func (s5 *socks5Conn) Serve() {
 	defer s5.Close()
+
 	if err := s5.handshake(); err != nil {
 		log.Println(err)
 		return
@@ -33,43 +60,50 @@ func (s5 *socks5Conn) handshake() error {
 	// only process auth methods here
 
 	buf := make([]byte, 258)
-	n, err := io.ReadAtLeast(s5.client_conn, buf, 1)
+
+	// read auth methods
+	n, err := io.ReadAtLeast(s5.clientConn, buf, 1)
 	if err != nil {
 		return err
 	}
 
 	l := int(buf[0]) + 1
 	if n < l {
-		_, err := io.ReadFull(s5.client_conn, buf[n:l])
+		// read remains data
+		_, err := io.ReadFull(s5.clientConn, buf[n:l])
 		if err != nil {
 			return err
 		}
 	}
 
 	// no auth required
-	s5.client_conn.Write([]byte{0x05, 0x00})
+	s5.clientConn.Write([]byte{0x05, 0x00})
 
 	return nil
 }
 
 func (s5 *socks5Conn) processRequest() error {
 	buf := make([]byte, 258)
-	n, err := io.ReadAtLeast(s5.client_conn, buf, 10)
+
+	// read header
+	n, err := io.ReadAtLeast(s5.clientConn, buf, 10)
 	if err != nil {
 		return err
 	}
+
 	if buf[0] != socks5Version {
-		return fmt.Errorf("error version %s", buf[0])
+		return fmt.Errorf("error version %d", buf[0])
 	}
 
-	// only support connect
+	// command only support connect
 	if buf[1] != cmdConnect {
 		return fmt.Errorf("unsupported command %s", buf[1])
 	}
 
-	hlen := 0
-	host := ""
-	msglen := 0
+	hlen := 0   // target address length
+	host := ""  // target address
+	msglen := 0 // header length
+
 	switch buf[3] {
 	case addrTypeIPv4:
 		hlen = 4
@@ -82,7 +116,8 @@ func (s5 *socks5Conn) processRequest() error {
 	msglen = 6 + hlen
 
 	if n < msglen {
-		_, err := io.ReadFull(s5.client_conn, buf[n:msglen])
+		// read remains header
+		_, err := io.ReadFull(s5.clientConn, buf[n:msglen])
 		if err != nil {
 			return err
 		}
@@ -96,18 +131,20 @@ func (s5 *socks5Conn) processRequest() error {
 		host = net.IP(addr).String()
 	}
 
+	// get target port
 	port := binary.BigEndian.Uint16(buf[msglen-2 : msglen])
 
+	// target address
 	target := net.JoinHostPort(host, fmt.Sprintf("%d", port))
 
 	// reply user with connect success
 	// if dial to target failed, user will receive connection reset
-	s5.client_conn.Write([]byte{0x05, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01})
+	s5.clientConn.Write([]byte{0x05, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x01, 0x01})
 
-	log.Printf("connecing to %s", target)
+	//log.Printf("connecing to %s\r\n", target)
 
 	// connect to the target
-	s5.server_conn, err = net.Dial("tcp", target)
+	s5.serverConn, err = s5.dial("tcp", target)
 	if err != nil {
 		return err
 	}
@@ -119,15 +156,27 @@ func (s5 *socks5Conn) processRequest() error {
 }
 
 func (s5 *socks5Conn) forward() {
-	go io.Copy(s5.client_conn, s5.server_conn)
-	io.Copy(s5.server_conn, s5.client_conn)
+
+	c := make(chan int, 2)
+
+	go func() {
+		io.Copy(s5.clientConn, s5.serverConn)
+		c <- 1
+	}()
+
+	go func() {
+		io.Copy(s5.serverConn, s5.clientConn)
+		c <- 1
+	}()
+
+	<-c
 }
 
 func (s5 *socks5Conn) Close() {
-	if s5.server_conn != nil {
-		s5.server_conn.Close()
+	if s5.serverConn != nil {
+		s5.serverConn.Close()
 	}
-	if s5.client_conn != nil {
-		s5.client_conn.Close()
+	if s5.clientConn != nil {
+		s5.clientConn.Close()
 	}
 }