How to implement FTP server and client in golang

FTP (File Transfer Protocol) is a commonly used file transfer protocol, usually used for file transfer between clients and servers. Go language is an efficient and concise programming language. Its powerful concurrency model and elegant syntax make it the first choice of many developers. This article will introduce how to use Go language to implement FTP server and client, making you more efficient in future development.

1. FTP protocol

FTP protocol includes two channels: control channel and data channel. The control channel is used to send instructions and receive responses, such as login, search, upload and download operations. The data channel is used to transfer files, including two transmission modes: ASCII mode and binary mode. ASCII mode is suitable for text file transfers, while binary mode is suitable for non-text file transfers.

The commonly used ports for FTP are 21 and 20, of which port 21 is used for control connections and port 20 is used for data connections. When the client initiates a connection, it will first connect to the FTP server on port 21 and send instructions to the server. The server then opens an ephemeral port for data transfer. The client connects to the server again and transmits data through the temporary port.

2. FTP server implementation

Using Go language to implement the FTP server, we need to implement the following functions:

1. User login and permission verification
2. Display the contents of the current directory
3. Switch directory
4. Delete files
5. Download files
6. Upload files

The specific implementation is as follows:

1. User login and permission verification

First, user login and permission verification functions need to be implemented. We can read the user list and passwords from a file and then check if the username and password entered by the user match. If the match is successful, the user object can be returned and saved to the session for subsequent calls.

2. Display the contents of the current directory

To display the contents of the current directory, we need to call the os package and io/ioutil package in the Go language to read all files in the current directory files and directories and return them to the client.

3. Switch directory

If the client wants to switch directories, we can first check whether the user has sufficient permissions to perform the switching operation. If so, we can use the os.Chdir() function to switch directories.

4. Delete files

If the client wants to delete the file, we need to use the os.Remove() function on the server to delete it. At the same time, we also need to check whether the client has sufficient permissions to perform the deletion operation.

5. Download file

When downloading a file, we need to first check whether the client has sufficient permissions to perform the download operation, and then send the file content in the data channel. We can use the io.Copy() function on the server to transfer the file contents to the client.

6. Upload files

When uploading files, we need to first check whether the client has sufficient permissions to perform the upload operation. Then receive the file content in the data channel and write it to the server. We can use the io.Copy() function on the server to save the data sent by the client to the specified directory.

3. FTP client implementation

Using Go language to implement the FTP client, we need to implement the following functions:

1. User login
2. Display Current directory content
3. Switch directory
4. Delete file
5. Download file
6. Upload file

The specific implementation is as follows:

1. User login

The client needs to enter a username and password and send them to the server for verification. If validation fails, the user needs to be prompted to re-enter.

2. Display the contents of the current directory

We can initiate a request to the server, obtain all files and directories in the current directory, and display them to the user.

3. Switch directory

If the user wants to switch directories, we need to send instructions and wait for the server to respond.

4. Delete File

If the user wants to delete the file, we need to send an instruction to the server and wait for the response.

5. Download file

When downloading a file, we need to send instructions to the server, receive the file content in the data channel, and save the file to the local disk.

6. Upload file

When uploading a file, we need to send instructions to the server and send the file content in the data channel.

4. Summary

Using Go language to implement FTP client and server can allow us to transfer files more efficiently. This article introduces the basic knowledge of FTP protocol and shows how to implement FTP client and server using Go language. I hope this article can help you better understand the FTP protocol and Go language, and refer to it in future development.

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