SMTP Server
To create an SMTP server program in Go, you need to create a few files: main.go for the main logic and optionally, a server.go file for the server functionality. Here is a step-by-step guide:
Step 1: Initialize the Go Module
First, create a new directory for your project and initialize the Go module.
mkdir smtpserver
cd smtpserver
go mod init github.com/username/smtpserver
Step 2: Create the server.go File
Create a server.go file to handle the SMTP server functionality.
// server.go
package main
import (
"log"
"net"
"github.com/emersion/go-smtp"
)
// Backend implements SMTP server methods.
type Backend struct{}
// Login handles login for the SMTP server.
func (bkd *Backend) Login(state *smtp.ConnectionState, username, password string) (smtp.Session, error) {
return &Session{}, nil
}
// AnonymousLogin allows anonymous login.
func (bkd *Backend) AnonymousLogin(state *smtp.ConnectionState) (smtp.Session, error) {
return &Session{}, nil
}
// A Session is returned after successful login.
type Session struct{}
// Mail handles the MAIL command.
func (s *Session) Mail(from string, opts smtp.MailOptions) error {
log.Println("Mail from:", from)
return nil
}
// Rcpt handles the RCPT command.
func (s *Session) Rcpt(to string) error {
log.Println("Rcpt to:", to)
return nil
}
// Data handles the DATA command.
func (s *Session) Data(r io.Reader) error {
log.Println("Data received")
return nil
}
// Reset handles the RSET command.
func (s *Session) Reset() {}
// Logout handles the LOGOUT command.
func (s *Session) Logout() error {
return nil
}
// StartServer starts the SMTP server on the specified port.
func StartServer(port string) error {
be := &Backend{}
s := smtp.NewServer(be)
s.Addr = ":" + port
s.Domain = "localhost"
s.ReadTimeout = 10 * time.Second
s.WriteTimeout = 10 * time.Second
s.MaxMessageBytes = 1024 * 1024
s.MaxRecipients = 50
s.AllowInsecureAuth = true
log.Println("Starting SMTP server on port", port)
return s.ListenAndServe()
}
Step 3: Create the main.go File
Create a main.go file to use the server functionality.
// main.go
package main
import (
"fmt"
"os"
)
func main() {
if len(os.Args) != 2 {
fmt.Println("Usage: smtpserver <port>")
os.Exit(1)
}
port := os.Args[1]
fmt.Printf("Starting SMTP server on port %s...\n", port)
if err := StartServer(port); err != nil {
fmt.Printf("Server failed: %v\n", err)
os.Exit(1)
}
}
Step 4: Run the Program
Run the program using the go run command.
go run main.go 2525
This will start the SMTP server on port 2525. You can connect to it using an SMTP client.
Last modified: 19 December 2024