Detailed explanation of how to implement SSH using Node.js

SSH is an encrypted network protocol that allows secure data communication between computers, especially for remote access and control.

Node.js is a JavaScript runtime environment based on the Chrome V8 engine, which can help us build efficient and scalable network applications. In this article, we will learn how to implement SSH using Node.js.

1. Installing Node.js

Before using Node.js, we need to install it first. You can download the installation package from the official website and follow the instructions to install it.

2. Install SSH2 module

In Node.js, we can use the SSH2 module to implement SSH. SSH2 is a pure JavaScript implementation of the SSH2 client and server-side library that runs in Node.js.

We can use the npm package manager to install the SSH2 module:

npm install ssh2

After the installation is complete, you can start using the SSH2 module.

3. Connect to SSH server

Before using the SSH2 module, we need to establish an SSH connection first.

const Client = require('ssh2').Client;

const conn = new Client();
conn.on('ready', () => {
  console.log('已连接');
  conn.end();
}).connect({
  host: 'x.x.x.x',
  port: 22,
  username: 'username',
  password: 'password',
});

In this example, we first import the Client class of the SSH2 module, and then create an SSH client connection object conn.

On the connection object, we can listen to the ready event, which is triggered after the connection is successfully established and outputs "connected" information. Finally, we call the conn.end() method to close the connection.

In the connection options, we need to provide the address, port, username and password information of the target SSH server.

4. Execute SSH commands

After the connection is successfully established, we can use the SSH2 module to execute remote commands.

conn.on('ready', () => {
  console.log('已连接');
  conn.exec('ls', (err, stream) => {
    if (err) throw err;
    stream.on('close', (code, signal) => {
      console.log(`命令执行结束，退出码为：${code}`);
      conn.end();
    }).on('data', data => {
      console.log(`输出信息：${data}`);
    }).stderr.on('data', data => {
      console.log(`错误信息：${data}`);
    });
  });
}).connect({
  host: 'x.x.x.x',
  port: 22,
  username: 'username',
  password: 'password',
});

In this example, we call the conn.exec() method to execute an ls command and pass in a callback function.

If an error occurs when executing the command, the callback function will throw an exception. If the command is executed successfully, we will get a readable stream object stream.

We can listen to the close event of the stream object, which is triggered at the end of the command execution and outputs the exit code. At the same time, we also listen to the data event and stderr event of the stream object, and output the standard output and error output information respectively.

Finally, we call the conn.end() method in the event handler function to close the connection.

5. File transfer

In addition to remote execution of commands, the SSH2 module also supports file transfer functions.

conn.sftp((err, sftp) => {
  if (err) throw err;
  const localFile = '/path/to/local/file.txt';
  const remoteFile = '/path/to/remote/file.txt';
  sftp.fastPut(localFile, remoteFile, err => {
    if (err) throw err;
    console.log('文件传输完成');
    conn.end();
  });
});

In this example, we call the conn.sftp() method to obtain an SFTP object, which provides file transfer functionality.

We use the sftp.fastPut() method to quickly transfer local files to the remote server. After the transfer is completed, we output the "File transfer completed" message and close the connection.

6. Summary

In this article, we learned how to implement SSH programmatically using the SSH2 module. We first connect to the SSH server and then perform commands and file transfers. With Node.js and the SSH2 module, we can easily implement SSH functionality for building efficient and scalable network applications.

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