Node.js socket.setTTL() 方法

socket.setTTL()方法是 dgram 模块中 Socket 类的内置应用程序编程接口，用于设置或清除IP_TTL套接字选项，该选项有助于指定允许数据包通过指定的 IP 跳数路由器或网关。

句法：

const socket.setTTL( ttl )

参数：此方法采用整数值，表示允许数据包通过指定路由器或网关的 IP 跳数。

返回值：此方法不返回任何值。

示例 1：文件名：index.js

Javascript

// Node.js program to demonstrate the
// server.setTTL() method
 
 
// Importing dgram module
var dgram = require('dgram');
 
// Creating and initializing client
// and server socket
var client = dgram.createSocket("udp4");
var server = dgram.createSocket("udp4");
let broadcast_address = 12345;
 
// Catching the message event
server.on("message", function (msg) {
 
  // Displaying the client message
  process.stdout.write("UDP String: " + msg + "\n");
 
  // Exiting process
  process.exit();
})
.bind(broadcast_address, () => {
 
  // Enable the IP_TTL socket option
  // and specifying the number of IP hopes
  // by using the setTTL() method
  server.setTTL(144);
});
 
// Client sending message to server
client.send("Hello", 0, 7, broadcast_address, "localhost");

输出：

UDP String: Hello

示例 2：文件名：index.js

Javascript

// Node.js program to demonstrate the
// server.setTTL() method
 
// Importing dgram module
var dgram = require('dgram');
 
// Creating and initializing client
// and server socket
var client = dgram.createSocket("udp4");
var server = dgram.createSocket("udp4");
 
// Catching the message event
server.on("message", function (msg) {
 
  // Displaying the client message
  process.stdout.write("UDP String: " + msg + "\n");
 
  // Exiting process
  process.exit();
});
 
// Catching the listening event
server.on('listening', () => {
  const address = server.address();
  console.log(`server listening
    ${address.address}:${address.port}`);
});
 
// Binding server with port address
server.bind(1234, () => {
    
  // Enable the IP_TTL socket option
  // and specifying the number of IP hopes
  // by using the setTTL() method
  server.setTTL(144);
});
 
// Client sending message to server
client.send("Hello", 0, 7, 1234, "localhost");

输出：

server listening 0.0.0.0:1234
UDP String: Hello

使用以下命令运行 index.js 文件：

node index.js

参考： https://nodejs.org/dist/latest-v12.x/docs/api/dgram.html#dgram_socket_settl_ttl