diff --git a/README.md b/README.md
index 560a768..276a4f2 100644
--- a/README.md
+++ b/README.md
@@ -170,6 +170,44 @@ trzsz-ssh ( tssh ) offers additional useful features:
 
 - Download from the [GitHub Releases](https://github.com/trzsz/trzsz-ssh/releases), unzip and add to `PATH` environment.
 
+## Development
+
+The `github.com/trzsz/trzsz-ssh/tssh` can be used as a library, for example:
+
+```go
+package main
+
+import (
+	"log"
+	"os"
+
+	"github.com/trzsz/trzsz-ssh/tssh"
+)
+
+func main() {
+	// Example 1: execute command on remote server
+	client, err := tssh.SshLogin(&tssh.SshArgs{Destination: "root@192.168.0.1"})
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer client.Close()
+	session, err := client.NewSession()
+	if err != nil {
+		log.Fatal(err)
+	}
+	defer session.Close()
+	output, err := session.CombinedOutput("whoami")
+	if err != nil {
+		log.Fatal(err)
+	}
+	log.Printf("I'm %s", string(output))
+
+	// Example 2: run the tssh program
+	code := tssh.TsshMain([]string{"-t", "root@192.168.0.1", "bash -l"})
+	os.Exit(code)
+}
+```
+
 ## Contributing
 
 Welcome and thank you for considering contributing. We appreciate all forms of support, from coding and testing to documentation and CI/CD improvements.
diff --git a/cmd/tssh/main.go b/cmd/tssh/main.go
index c11eecd..71ae1b2 100644
--- a/cmd/tssh/main.go
+++ b/cmd/tssh/main.go
@@ -31,5 +31,5 @@ import (
 )
 
 func main() {
-	os.Exit(tssh.TsshMain())
+	os.Exit(tssh.TsshMain(os.Args[1:]))
 }
diff --git a/tssh/agent.go b/tssh/agent.go
index baed36c..d05fe97 100644
--- a/tssh/agent.go
+++ b/tssh/agent.go
@@ -88,7 +88,7 @@ func getAgentClient(args *sshArgs, param *sshParam) agent.ExtendedAgent {
 	return agentClient
 }
 
-func forwardToRemote(client sshClient, addr string) error {
+func forwardToRemote(client SshClient, addr string) error {
 	channels := client.HandleChannelOpen(kAgentChannelType)
 	if channels == nil {
 		return fmt.Errorf("agent: already have handler for %s", kAgentChannelType)
@@ -122,7 +122,7 @@ func forwardAgentRequest(channel ssh.Channel, addr string) {
 	forwardChannel(channel, conn)
 }
 
-func requestAgentForwarding(session sshSession) error {
+func requestAgentForwarding(session SshSession) error {
 	ok, err := session.SendRequest(kAgentRequestName, true, nil)
 	if err != nil {
 		return err
diff --git a/tssh/config.go b/tssh/config.go
index b20b4a6..d3a293a 100644
--- a/tssh/config.go
+++ b/tssh/config.go
@@ -94,7 +94,7 @@ type tsshConfig struct {
 	wildcardPatterns    []*ssh_config.Pattern
 }
 
-var userConfig = &tsshConfig{}
+var userConfig *tsshConfig
 
 func parseTsshConfig() {
 	path := filepath.Join(userHomeDir, ".tssh.conf")
@@ -218,8 +218,8 @@ func showTsshConfig() {
 	}
 }
 
-func initUserConfig(configFile string) error {
-	var err error
+func initUserConfig(configFile string) (err error) {
+	userConfig = &tsshConfig{}
 	userHomeDir, err = os.UserHomeDir()
 	if err != nil {
 		debug("user home dir failed: %v", err)
diff --git a/tssh/ctrl_unix.go b/tssh/ctrl_unix.go
index 8309524..2f42e69 100644
--- a/tssh/ctrl_unix.go
+++ b/tssh/ctrl_unix.go
@@ -318,7 +318,7 @@ func startControlMaster(args *sshArgs, sshPath string) error {
 	return nil
 }
 
-func connectViaControl(args *sshArgs, param *sshParam) sshClient {
+func connectViaControl(args *sshArgs, param *sshParam) SshClient {
 	ctrlMaster := getOptionConfig(args, "ControlMaster")
 	ctrlPath := getOptionConfig(args, "ControlPath")
 
diff --git a/tssh/ctrl_windows.go b/tssh/ctrl_windows.go
index 7171e90..7beb1b3 100644
--- a/tssh/ctrl_windows.go
+++ b/tssh/ctrl_windows.go
@@ -28,7 +28,7 @@ import (
 	"strings"
 )
 
-func connectViaControl(args *sshArgs, param *sshParam) sshClient {
+func connectViaControl(args *sshArgs, param *sshParam) SshClient {
 	ctrlMaster := getOptionConfig(args, "ControlMaster")
 	ctrlPath := getOptionConfig(args, "ControlPath")
 
diff --git a/tssh/env.go b/tssh/env.go
index b07a4e2..8822f4f 100644
--- a/tssh/env.go
+++ b/tssh/env.go
@@ -118,7 +118,7 @@ func getSetEnvs(args *sshArgs) ([]*sshEnv, error) {
 	return envs, nil
 }
 
-func sendAndSetEnv(args *sshArgs, session sshSession) (string, error) {
+func sendAndSetEnv(args *sshArgs, session SshSession) (string, error) {
 	sendEnvs, err := getSendEnvs(args)
 	if err != nil {
 		return "", err
diff --git a/tssh/forward.go b/tssh/forward.go
index 3e74cfc..2f34728 100644
--- a/tssh/forward.go
+++ b/tssh/forward.go
@@ -227,7 +227,7 @@ func listenOnLocal(args *sshArgs, addr *string, port string) (listeners []net.Li
 	return
 }
 
-func listenOnRemote(args *sshArgs, client sshClient, addr *string, port string) (listeners []net.Listener) {
+func listenOnRemote(args *sshArgs, client SshClient, addr *string, port string) (listeners []net.Listener) {
 	listen := func(network, address string) {
 		listener, err := client.Listen(network, address)
 		if err != nil {
@@ -251,7 +251,7 @@ func listenOnRemote(args *sshArgs, client sshClient, addr *string, port string)
 	return
 }
 
-func stdioForward(client sshClient, addr string) (*sync.WaitGroup, error) {
+func stdioForward(client SshClient, addr string) (*sync.WaitGroup, error) {
 	conn, err := client.DialTimeout("tcp", addr, 10*time.Second)
 	if err != nil {
 		return nil, fmt.Errorf("stdio forward failed: %v", err)
@@ -283,7 +283,7 @@ func (d sshResolver) Resolve(ctx context.Context, name string) (context.Context,
 	return ctx, []byte{}, nil
 }
 
-func dynamicForward(client sshClient, b *bindCfg, args *sshArgs) {
+func dynamicForward(client SshClient, b *bindCfg, args *sshArgs) {
 	server, err := socks5.New(&socks5.Config{
 		Resolver: &sshResolver{},
 		Dial: func(ctx context.Context, network, addr string) (net.Conn, error) {
@@ -334,7 +334,7 @@ func netForward(local, remote net.Conn) {
 	<-done
 }
 
-func localForward(client sshClient, f *forwardCfg, args *sshArgs) {
+func localForward(client SshClient, f *forwardCfg, args *sshArgs) {
 	remoteAddr := joinHostPort(f.destHost, strconv.Itoa(f.destPort))
 	for _, listener := range listenOnLocal(args, f.bindAddr, strconv.Itoa(f.bindPort)) {
 		go func(listener net.Listener) {
@@ -360,7 +360,7 @@ func localForward(client sshClient, f *forwardCfg, args *sshArgs) {
 	}
 }
 
-func remoteForward(client sshClient, f *forwardCfg, args *sshArgs) {
+func remoteForward(client SshClient, f *forwardCfg, args *sshArgs) {
 	localAddr := joinHostPort(f.destHost, strconv.Itoa(f.destPort))
 	for _, listener := range listenOnRemote(args, client, f.bindAddr, strconv.Itoa(f.bindPort)) {
 		go func(listener net.Listener) {
@@ -386,7 +386,7 @@ func remoteForward(client sshClient, f *forwardCfg, args *sshArgs) {
 	}
 }
 
-func sshForward(client sshClient, args *sshArgs, param *sshParam) error {
+func sshForward(client SshClient, args *sshArgs, param *sshParam) error {
 	// clear all forwardings
 	if strings.ToLower(getOptionConfig(args, "ClearAllForwardings")) == "yes" {
 		return nil
@@ -451,7 +451,7 @@ type x11Request struct {
 	ScreenNumber     uint32
 }
 
-func sshX11Forward(args *sshArgs, client sshClient, session sshSession) {
+func sshX11Forward(args *sshArgs, client SshClient, session SshSession) {
 	if args.NoX11Forward || !args.X11Untrusted && !args.X11Trusted && strings.ToLower(getOptionConfig(args, "ForwardX11")) != "yes" {
 		return
 	}
diff --git a/tssh/login.go b/tssh/login.go
index 19f469b..c557f94 100644
--- a/tssh/login.go
+++ b/tssh/login.go
@@ -992,7 +992,7 @@ func getNetworkAddressFamily(args *sshArgs) string {
 	}
 }
 
-func sshConnect(args *sshArgs, client sshClient, proxy string) (sshClient, *sshParam, bool, error) {
+func sshConnect(args *sshArgs, client SshClient, proxy string) (SshClient, *sshParam, bool, error) {
 	param, err := getSshParam(args)
 	if err != nil {
 		return nil, nil, false, err
@@ -1028,7 +1028,7 @@ func sshConnect(args *sshArgs, client sshClient, proxy string) (sshClient, *sshP
 
 	network := getNetworkAddressFamily(args)
 
-	proxyConnect := func(client sshClient, proxy string) (sshClient, *sshParam, bool, error) {
+	proxyConnect := func(client SshClient, proxy string) (SshClient, *sshParam, bool, error) {
 		debug("login to [%s], addr: %s", args.Destination, param.addr)
 		conn, err := client.DialTimeout(network, param.addr, 10*time.Second)
 		if err != nil {
@@ -1078,7 +1078,7 @@ func sshConnect(args *sshArgs, client sshClient, proxy string) (sshClient, *sshP
 	}
 
 	// has proxies
-	var proxyClient sshClient
+	var proxyClient SshClient
 	for _, proxy = range param.proxy {
 		proxyClient, _, _, err = sshConnect(&sshArgs{Destination: proxy}, proxyClient, proxy)
 		if err != nil {
@@ -1088,7 +1088,7 @@ func sshConnect(args *sshArgs, client sshClient, proxy string) (sshClient, *sshP
 	return proxyConnect(proxyClient, proxy)
 }
 
-func keepAlive(client sshClient, args *sshArgs) {
+func keepAlive(client SshClient, args *sshArgs) {
 	getOptionValue := func(option string) int {
 		value, err := strconv.Atoi(getOptionConfig(args, option))
 		if err != nil {
@@ -1129,7 +1129,7 @@ func keepAlive(client sshClient, args *sshArgs) {
 	}()
 }
 
-func sshAgentForward(args *sshArgs, param *sshParam, client sshClient, session sshSession) {
+func sshAgentForward(args *sshArgs, param *sshParam, client SshClient, session SshSession) {
 	if args.NoForwardAgent || !args.ForwardAgent && strings.ToLower(getOptionConfig(args, "ForwardAgent")) != "yes" {
 		return
 	}
diff --git a/tssh/main.go b/tssh/main.go
index 68f8d9b..294b444 100644
--- a/tssh/main.go
+++ b/tssh/main.go
@@ -116,9 +116,16 @@ func cleanupAfterLogin() {
 
 var isTerminal bool = isatty.IsTerminal(os.Stdin.Fd()) || isatty.IsCygwinTerminal(os.Stdin.Fd())
 
-func TsshMain() int {
+// TrzMain is the main function of tssh program.
+func TsshMain(argv []string) int {
+	// parse ssh args
 	var args sshArgs
-	parser := arg.MustParse(&args)
+	parser, err := arg.NewParser(arg.Config{Out: os.Stderr, Exit: os.Exit}, &args)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, err)
+		return -1
+	}
+	parser.MustParse(argv)
 
 	// debug log
 	if args.Debug {
@@ -129,7 +136,6 @@ func TsshMain() int {
 	defer cleanupOnExit()
 
 	// print message after stdin reset
-	var err error
 	defer func() {
 		if err != nil {
 			fmt.Fprintf(os.Stderr, "%v\r\n", err)
@@ -149,7 +155,7 @@ func TsshMain() int {
 	}
 
 	// execute local tools if necessary
-	if code, quit := execLocalTools(&args); quit {
+	if code, quit := execLocalTools(argv, &args); quit {
 		return code
 	}
 
diff --git a/tssh/ssh.go b/tssh/ssh.go
index 0131e90..b00be0c 100644
--- a/tssh/ssh.go
+++ b/tssh/ssh.go
@@ -28,6 +28,7 @@ import (
 	"fmt"
 	"io"
 	"net"
+	"strings"
 	"time"
 
 	"golang.org/x/crypto/ssh"
@@ -40,36 +41,169 @@ const (
 	kAgentRequestName = "auth-agent-req@openssh.com"
 )
 
-type sshClient interface {
+// SshClient implements a traditional SSH client that supports shells,
+// subprocesses, TCP port/streamlocal forwarding and tunneled dialing.
+type SshClient interface {
+
+	// Wait blocks until the connection has shut down.
 	Wait() error
+
+	// Close closes the underlying network connection.
 	Close() error
-	NewSession() (sshSession, error)
+
+	// NewSession opens a new Session for this client.
+	NewSession() (SshSession, error)
+
+	// DialTimeout initiates a connection to the addr from the remote host.
 	DialTimeout(network, addr string, timeout time.Duration) (net.Conn, error)
+
+	// Listen requests the remote peer open a listening socket on addr.
 	Listen(network, addr string) (net.Listener, error)
+
+	// HandleChannelOpen returns a channel on which NewChannel requests
+	// for the given type are sent. If the type already is being handled,
+	// nil is returned. The channel is closed when the connection is closed.
 	HandleChannelOpen(channelType string) <-chan ssh.NewChannel
+
+	// SendRequest sends a global request, and returns the reply.
 	SendRequest(name string, wantReply bool, payload []byte) (bool, []byte, error)
 }
 
-type sshSession interface {
+// SshSession represents a connection to a remote command or shell.
+type SshSession interface {
+
+	// Wait waits for the remote command to exit.
 	Wait() error
+
+	// Close closes the underlying network connection.
 	Close() error
+
+	// Shell starts a login shell on the remote host.
 	Shell() error
+
+	// Run runs cmd on the remote host.
 	Run(cmd string) error
+
+	// Start runs cmd on the remote host.
 	Start(cmd string) error
+
+	// WindowChange informs the remote host about a terminal window dimension
+	// change to height rows and width columns.
 	WindowChange(height, width int) error
+
+	// Setenv sets an environment variable that will be applied to any
+	// command executed by Shell or Run.
 	Setenv(name, value string) error
+
+	// StdinPipe returns a pipe that will be connected to the
+	// remote command's standard input when the command starts.
 	StdinPipe() (io.WriteCloser, error)
+
+	// StdoutPipe returns a pipe that will be connected to the
+	// remote command's standard output when the command starts.
 	StdoutPipe() (io.Reader, error)
+
+	// StderrPipe returns a pipe that will be connected to the
+	// remote command's standard error when the command starts.
 	StderrPipe() (io.Reader, error)
+
+	// Output runs cmd on the remote host and returns its standard output.
 	Output(cmd string) ([]byte, error)
+
+	// CombinedOutput runs cmd on the remote host and returns its combined
+	// standard output and standard error.
 	CombinedOutput(cmd string) ([]byte, error)
+
+	// RequestPty requests the association of a pty with the session on the remote host.
 	RequestPty(term string, height, width int, termmodes ssh.TerminalModes) error
+
+	// SendRequest sends an out-of-band channel request on the SSH channel
+	// underlying the session.
 	SendRequest(name string, wantReply bool, payload []byte) (bool, error)
 }
 
+// SshArgs specifies the arguments to log in to the remote server.
+type SshArgs struct {
+
+	// Destination specifies the remote server to log in to.
+	// e.g., alias in ~/.ssh/config, [user@]hostname[:port].
+	Destination string
+
+	// IPv4Only forces ssh to use IPv4 addresses only
+	IPv4Only bool
+
+	// IPv6Only forces ssh to use IPv6 addresses only
+	IPv6Only bool
+
+	// Port to connect to on the remote host
+	Port int
+
+	// LoginName specifies the user to log in as on the remote machine
+	LoginName string
+
+	// Identity selects the identity (private key) for public key authentication
+	Identity []string
+
+	// CipherSpec specifies the cipher for encrypting the session
+	CipherSpec string
+
+	// ConfigFile specifies the per-user configuration file
+	ConfigFile string
+
+	// ProxyJump specifies the jump hosts separated by comma characters
+	ProxyJump string
+
+	// Option gives options in the format used in the configuration file
+	Option map[string][]string
+
+	// Debug causes ssh to print debugging messages about its progress
+	Debug bool
+
+	// Udp means using UDP protocol ( QUIC / KCP ) connection like mosh
+	Udp bool
+
+	// TsshdPath specifies the tsshd absolute path on the server
+	TsshdPath string
+}
+
+// SshLogin logs in to the remote server and creates a Client.
+func SshLogin(args *SshArgs) (SshClient, error) {
+	options := make(map[string][]string)
+	for key, values := range args.Option {
+		name := strings.ToLower(key)
+		if _, ok := options[name]; ok {
+			return nil, fmt.Errorf("option %s is repeated", name)
+		}
+		options[name] = values
+	}
+	if err := initUserConfig(args.ConfigFile); err != nil {
+		return nil, err
+	}
+	ss, err := sshLogin(&sshArgs{
+		NoCommand:   true,
+		Destination: args.Destination,
+		IPv4Only:    args.IPv4Only,
+		IPv6Only:    args.IPv6Only,
+		Port:        args.Port,
+		LoginName:   args.LoginName,
+		Identity:    multiStr{args.Identity},
+		CipherSpec:  args.CipherSpec,
+		ConfigFile:  args.ConfigFile,
+		ProxyJump:   args.ProxyJump,
+		Option:      sshOption{options},
+		Debug:       args.Debug,
+		Udp:         args.Udp,
+		TsshdPath:   args.TsshdPath,
+	})
+	if err != nil {
+		return nil, err
+	}
+	return ss.client, nil
+}
+
 type sshClientSession struct {
-	client    sshClient
-	session   sshSession
+	client    SshClient
+	session   SshSession
 	serverIn  io.WriteCloser
 	serverOut io.Reader
 	serverErr io.Reader
@@ -101,7 +235,7 @@ func (c *sshClientWrapper) Close() error {
 	return c.client.Close()
 }
 
-func (c *sshClientWrapper) NewSession() (sshSession, error) {
+func (c *sshClientWrapper) NewSession() (SshSession, error) {
 	return c.client.NewSession()
 }
 
@@ -132,7 +266,7 @@ func (c *sshClientWrapper) SendRequest(name string, wantReply bool, payload []by
 	return c.client.SendRequest(name, wantReply, payload)
 }
 
-func sshNewClient(c ssh.Conn, chans <-chan ssh.NewChannel, reqs <-chan *ssh.Request) sshClient {
+func sshNewClient(c ssh.Conn, chans <-chan ssh.NewChannel, reqs <-chan *ssh.Request) SshClient {
 	client := ssh.NewClient(c, chans, reqs)
 	return &sshClientWrapper{client}
 }
diff --git a/tssh/tools.go b/tssh/tools.go
index 6bee9de..c18a62f 100644
--- a/tssh/tools.go
+++ b/tssh/tools.go
@@ -448,14 +448,14 @@ func isFileNotExistOrEmpty(path string) bool {
 //
 // return true to quit with return code
 // return false to continue ssh login
-func execLocalTools(args *sshArgs) (int, bool) {
+func execLocalTools(argv []string, args *sshArgs) (int, bool) {
 	switch {
 	case args.Ver:
 		fmt.Println(args.Version())
 		return 0, true
 	case args.EncSecret:
 		return execEncodeSecret()
-	case args.NewHost || len(os.Args) == 1 && isFileNotExistOrEmpty(userConfig.configPath):
+	case args.NewHost || len(argv) == 0 && isFileNotExistOrEmpty(userConfig.configPath):
 		return execNewHost(args)
 	default:
 		return 0, false
@@ -463,7 +463,7 @@ func execLocalTools(args *sshArgs) (int, bool) {
 }
 
 // execRemoteTools execute remote tools if necessary
-func execRemoteTools(args *sshArgs, client sshClient) {
+func execRemoteTools(args *sshArgs, client SshClient) {
 	switch {
 	case args.InstallTrzsz:
 		execInstallTrzsz(args, client)
diff --git a/tssh/tools_install_trzsz.go b/tssh/tools_install_trzsz.go
index 9ca0966..67f9dda 100644
--- a/tssh/tools_install_trzsz.go
+++ b/tssh/tools_install_trzsz.go
@@ -70,7 +70,7 @@ func getLatestTrzszVersion() (string, error) {
 	return release.TagName[1:], nil
 }
 
-func checkTrzszVersion(client sshClient, cmd, name, version string) bool {
+func checkTrzszVersion(client SshClient, cmd, name, version string) bool {
 	session, err := client.NewSession()
 	if err != nil {
 		return false
@@ -91,16 +91,16 @@ func pathJoin(path, name string) string {
 	return fmt.Sprintf("%s/%s", path, name)
 }
 
-func checkInstalledVersion(client sshClient, path, name, version string) bool {
+func checkInstalledVersion(client SshClient, path, name, version string) bool {
 	cmd := fmt.Sprintf("%s -v", pathJoin(path, name))
 	return checkTrzszVersion(client, cmd, name, version)
 }
 
-func checkTrzszExecutable(client sshClient, name, version string) bool {
+func checkTrzszExecutable(client SshClient, name, version string) bool {
 	return checkTrzszVersion(client, fmt.Sprintf("$SHELL -l -c '%s -v'", name), name, version)
 }
 
-func checkTrzszPathEnv(client sshClient, version, path string) {
+func checkTrzszPathEnv(client SshClient, version, path string) {
 	trzExecutable := checkTrzszExecutable(client, "trz", version)
 	tszExecutable := checkTrzszExecutable(client, "tsz", version)
 	if !trzExecutable || !tszExecutable {
@@ -108,7 +108,7 @@ func checkTrzszPathEnv(client sshClient, version, path string) {
 	}
 }
 
-func getRemoteUserHome(client sshClient) (string, error) {
+func getRemoteUserHome(client SshClient) (string, error) {
 	session, err := client.NewSession()
 	if err != nil {
 		return "", err
@@ -135,7 +135,7 @@ func getRemoteUserHome(client sshClient) (string, error) {
 	return "~", nil
 }
 
-func getRemoteServerOS(client sshClient) (string, error) {
+func getRemoteServerOS(client SshClient) (string, error) {
 	session, err := client.NewSession()
 	if err != nil {
 		return "", err
@@ -156,7 +156,7 @@ func getRemoteServerOS(client sshClient) (string, error) {
 	}
 }
 
-func getRemoteServerArch(client sshClient) (string, error) {
+func getRemoteServerArch(client SshClient) (string, error) {
 	session, err := client.NewSession()
 	if err != nil {
 		return "", err
@@ -183,7 +183,7 @@ func getRemoteServerArch(client sshClient) (string, error) {
 	}
 }
 
-func mkdirInstallPath(client sshClient, path string) error {
+func mkdirInstallPath(client SshClient, path string) error {
 	session, err := client.NewSession()
 	if err != nil {
 		return err
@@ -306,7 +306,7 @@ func readTrzszBinary(path, version, svrOS, arch string) ([]byte, []byte, error)
 	return extractTrzszBinary(gzr, version, svrOS, arch)
 }
 
-func uploadTrzszBinary(client sshClient, path string, trz, tsz []byte) error {
+func uploadTrzszBinary(client SshClient, path string, trz, tsz []byte) error {
 	session, err := client.NewSession()
 	if err != nil {
 		return err
@@ -403,7 +403,7 @@ func uploadTrzszBinary(client sshClient, path string, trz, tsz []byte) error {
 	return nil
 }
 
-func execInstallTrzsz(args *sshArgs, client sshClient) {
+func execInstallTrzsz(args *sshArgs, client SshClient) {
 	version := args.TrzszVersion
 	if version == "" {
 		var err error
diff --git a/tssh/udp.go b/tssh/udp.go
index dfec9b6..d938fed 100644
--- a/tssh/udp.go
+++ b/tssh/udp.go
@@ -127,7 +127,7 @@ func (c *sshUdpClient) Close() error {
 	return c.client.Close()
 }
 
-func (c *sshUdpClient) NewSession() (sshSession, error) {
+func (c *sshUdpClient) NewSession() (SshSession, error) {
 	stream, err := c.newStream("session")
 	if err != nil {
 		return nil, err