How to use network programming functions in Go language to implement multi-user login verification and permission control on FTP server?

How to use network programming functions in Go language to implement multi-user login verification and permission control of FTP server?

FTP (File Transfer Protocol) is a standard network protocol for file transfer. In practical applications, we often need to implement multi-user login verification and permission control for FTP servers. This article will introduce how to use the network programming functions of the Go language to implement an FTP server and implement multi-user login verification and permission control functions. The following is a detailed code example:

First, we need to import the corresponding package:

import (
    "fmt"
    "net"
    "strings"
)

Next, we define a global user list to store the usernames and passwords of different users:

var userList = map[string]string{
    "user1": "password1",
    "user2": "password2",
}

Then, we implement a function that handles the connection:

func handleConnection(conn net.Conn) {
    defer conn.Close()

    for {
        // 读取客户端发送的命令
        buffer := make([]byte, 1024)
        n, err := conn.Read(buffer)
        if err != nil {
            fmt.Println("Error reading:", err.Error())
            break
        }

        // 解析并执行命令
        command := strings.TrimSpace(string(buffer[:n]))
        if strings.HasPrefix(command, "USER ") {
            user := strings.TrimSpace(strings.TrimPrefix(command, "USER "))
            // 验证用户登录
            if password, ok := userList[user]; ok {
                conn.Write([]byte("331 Password required for " + user + "
"))
                // TODO：等待用户输入密码并进行验证
            } else {
                conn.Write([]byte("530 Login incorrect
"))
            }
        } else {
            conn.Write([]byte("500 Unknown command
"))
        }
    }
}

In the above code, we utilize the strings.HasPrefix function and strings.TrimPrefixFunction to parse the command sent by the client. When the client sends the USER command, we first extract the user name and perform login verification. If the username does not exist or the password is incorrect, we send a login failure message to the client; if the username exists and the password is correct, we send a message asking for a password to the client.

It should be noted that the above code only implements the login verification part. The verification of the password still needs to be implemented. The encryption algorithm can be used to encrypt the password and compare it according to actual needs.

Finally, we write the main function to listen to the specified port and accept client connections:

func main() {
    listener, err := net.Listen("tcp", "localhost:21")
    if err != nil {
        fmt.Println("Error listening:", err.Error())
        return
    }
    defer listener.Close()

    fmt.Println("FTP server is listening on localhost:21")

    for {
        conn, err := listener.Accept()
        if err != nil {
            fmt.Println("Error accepting:", err.Error())
            break
        }

        go handleConnection(conn)
    }
}

In the main function, we use the net.Listen function to listen to a specific address and port, and wait in a loop to accept client connections. When a client connects successfully, we use the go keyword to open a new coroutine to handle the connection.

Through the above code examples, we have implemented a simple FTP server, and implemented the functions of multi-user login verification and permission control based on the network programming functions of the Go language. You can expand it according to actual needs, such as: controlling permissions for users to upload and download files, implementing directory changes, file deletion and other functions. I hope this article will help you understand the network programming functions in the Go language and implement multi-user login verification and permission control on the FTP server.

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