Nodejs determines whether the agent is available

With the popularity of the Internet, the demand for using proxies is also getting higher and higher. Understanding whether the proxy is available is a very important step. It is related to whether we can safely use the proxy to surf the Internet. This article will introduce how to use Node.js to determine whether the proxy is available.

1. What is a proxy

A proxy is a method of network communication. In layman's terms, it is a middleman who forwards our requests to the server and then returns the response to us. Proxies can be divided into forward proxies and reverse proxies.

Forward proxy means that the client sends the request to the proxy, and then the proxy sends it to the target server, and returns the server's response to the client.

Reverse proxy means that the server sends the request to the proxy, and the proxy sends the request to the client and returns the client's response to the server. Reverse proxies can be used for load balancing, added security, and more.

2. Why use a proxy

There are many benefits of using a proxy:

1. Hide the real IP address. Some websites or apps are restricted to specific IP addresses, and if you have multiple IP addresses, you can use a proxy to easily access them.

2. Using a proxy can better protect your privacy. A proxy can provide you with a safer browsing experience because the proxy server can hide your real IP address and what you are accessing.

3. Proxy can help you access blocked websites. In some countries or regions, governments or other agencies may block access to certain websites. If you use a restricted IP address, you will not be able to access these websites. In this case, you can use a proxy to access them.

3. How to determine whether the agent is available

Using Node.js, you can easily determine whether the agent is available. The specific method is introduced below.

1. Use the http module to detect whether the proxy is available.

Using the http module can easily test the proxy. The specific code is as follows:

const http = require('http');

// 可用代理列表
const proxyList = [
  'http://127.0.0.1:8080',
  'http://127.0.0.1:8888',
  'http://127.0.0.1:1080',
];

// 请求目标地址
const options = {
  host: 'www.baidu.com',
  port: 80,
  path: '/',
  method: 'GET'
};

// 测试代理是否可用
const testProxy = (proxy) => {
  const req = http.request(options);

  req.setTimeout(1000, () => {
    console.log(`${proxy} timeout`);
    req.abort();
  });

  req.on('error', (error) => {
    console.log(`${proxy} error: ${error.message}`);
  });

  req.on('response', (res) => {
    console.log(`${proxy} statusCode: ${res.statusCode}`);
  });

  // 将请求发送到代理服务器
  req.end();
};

// 检测代理
proxyList.forEach((proxy) => {
  testProxy(proxy);
});

In the above code, first define The proxy server list and target address are then defined, and the testProxy function is used to detect whether the proxy is available. In the testProxy function, use the http.request method to send a request to the target address. If the request is successful, the proxy is available. Otherwise, the agent is unavailable.

Finally, loop through the proxy server list and test each proxy in turn.

2. Use the request module to detect whether the proxy is available

Compared with the http module, the request module is simpler to use and more powerful. The following is the specific code for using the request module to detect the proxy:

const request = require('request');

// 可用代理列表
const proxyList = [
  'http://127.0.0.1:8080',
  'http://127.0.0.1:8888',
  'http://127.0.0.1:1080',
];

// 请求目标地址
const options = {
  url: 'https://www.baidu.com',
  method: 'GET'
};

// 测试代理是否可用
const testProxy = (proxy) => {
  options.proxy = proxy;

  request(options, (error, res, body) => {
    if (error) {
      console.log(`${proxy} error: ${error.message}`);
    } else {
      console.log(`${proxy} statusCode: ${res.statusCode}`);
    }
  });
};

// 检测代理
proxyList.forEach((proxy) => {
  testProxy(proxy);
});

In the above code, the proxy server list and target address are first defined, and then the testProxy function is defined to detect whether the proxy is available. In the testProxy function, use the request method to send a request to the target address and set the proxy to the proxy currently being tested. If the request succeeds, the proxy is available. Otherwise, the agent is unavailable.

Finally, loop through the proxy server list and test each proxy in turn.

4. Summary

This article introduces how to use Node.js to quickly detect whether the agent is available. Using the above method, you can easily test the proxy and select an available proxy server for Internet access. When using a proxy server, you need to pay attention to security and stability to avoid security issues and network disconnections.

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