feat: add ascii diagram to tunnel creation message

diagram.txt

@@ -0,0 +1,7 @@
+                                    NAT                                    NAT
+  My machine                         |       {{ .Hostname }}        |       Remote Machine
+ +----------+                        |            +----------+              |        +----------+
+ |          |<local_service_port>    |        {{.Pp}}|          |{{.Pp}}          |  {{.Rp}}|          |
+ |          +<-----------------------+----------->+          +<-------------+------->+          |
+ +----------+                        |            +----------+              |        +----------+
+                                     |                                      |

modd.conf

@@ -1,4 +1,6 @@
 **/*.go
+diagram.txt
+.env
 Makefile {
     prep: make build
     daemon: make run

session_handler.go

@@ -1,13 +1,23 @@
 package rebound
 
 import (
+	"bytes"
 	"fmt"
 	"io"
+	"log"
+	"strings"
+	"text/template"
+
+	_ "embed"
 
 	"github.com/gliderlabs/ssh"
 	"github.com/pkg/errors"
 )
 
+//go:embed diagram.txt
+var asciiDiagram string
+var asciiDiagramTmpl = template.Must(template.New("").Parse(asciiDiagram))
+
 func (s *Server) handleSession(sess ssh.Session) {
 	ctx := sess.Context()
 	sessionID := SessionID(ctx.SessionID())
@@ -15,9 +25,7 @@ func (s *Server) handleSession(sess ssh.Session) {
 	s.log("(%s): session opened", sessionID)
 
 	message := `
-Welcome on Rebound !
-
-Type Ctrl+C or Ctrl+D to exit.
+	Welcome on Rebound !
 `
 
 	if _, err := sess.Write([]byte(message)); err != nil {
@@ -71,7 +79,9 @@ func (s *Server) handleSessionData(sess ssh.Session, data SessionData) error {
 }
 
 func (s *Server) writeConsumerMessage(sess ssh.Session, data SessionData) error {
-	message := ``
+	message := `
+	Type Ctrl+C or Ctrl+D to exit.
+	`
 
 	if _, err := sess.Write([]byte(message)); err != nil {
 		return errors.WithStack(err)
@@ -81,12 +91,46 @@ func (s *Server) writeConsumerMessage(sess ssh.Session, data SessionData) error
 }
 
 func (s *Server) writeProviderMessage(sess ssh.Session, data SessionData) error {
+	var diagramBuff bytes.Buffer
+
+	hostname := s.opts.PublicHost
+	if len(hostname) < 24 {
+		halfPadding := (24 - len(hostname)) / 2
+		leftPadding := strings.Repeat(" ", halfPadding)
+		rightPadding := strings.Repeat(" ", halfPadding)
+		hostname = fmt.Sprintf("%s%s%s", leftPadding, hostname, rightPadding)
+		if len(hostname) > 24 {
+			hostname = hostname[0:23]
+		}
+	} else if len(hostname) >= 24 {
+		hostname = hostname[0:20] + "..."
+	}
+
+	log.Printf("'%s'", hostname)
+
+	tmplData := struct {
+		Pp       string
+		Rp       string
+		Hostname string
+	}{
+		Pp:       fmt.Sprintf("%04d", s.opts.PublicPort),
+		Rp:       "<port>",
+		Hostname: hostname,
+	}
+
+	if err := asciiDiagramTmpl.Execute(&diagramBuff, tmplData); err != nil {
+		return errors.WithStack(err)
+	}
+
 	message := fmt.Sprintf(`
-You can connect to your tunnel by running in an other terminal:
+	You can connect to your tunnel by running in an other terminal:
 
-ssh -L <local-port>:0.0.0.0:1 %s@%s -p %d
+	ssh -L <port>:127.0.0.1:1 %s@%s -p %d
 
-`, data.Token, s.opts.PublicHost, s.opts.PublicPort)
+%s
+
+	Type Ctrl+C or Ctrl+D to exit.
+`, data.Token, s.opts.PublicHost, s.opts.PublicPort, diagramBuff.String())
 
 	if _, err := sess.Write([]byte(message)); err != nil {
 		return errors.WithStack(err)