Node.js socket.setMulticastTTL() 方法

socket.setMulticastTTL() 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_MULTICAST_TTL套接字选项，该选项有助于指定允许数据包通过指定多播传输的 IP 跳数交通。

句法：

const socket.setMulticastTTL( ttl )

参数：此方法采用整数值，表示允许数据包通过指定多播流量的 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.setMulticastTTL()  API
 
// 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;
 
// Handling 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_MULTICAST_TTL socket option
  // and specifying the number of IP hopes
  // by using the setMulticastTTL() method
  server.setMulticastTTL(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.setMulticastTTL()  API
 
// Importing dgram module
var dgram = require('dgram');
 
// Creating and initializing client
// and server socket
var client = dgram.createSocket("udp4");
var server = dgram.createSocket("udp4");
 
// Handling the message event
server.on("message", function (msg) {
 
  // Displaying the client message
  process.stdout.write("UDP String: "
                       + msg + "\n");
 
  // Exiting process
  process.exit();
 
});
 
// Handling 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_MULTICAST_TTL socket option
   // and specifying the number of IP hopes
   // by using the setMulticastTTL() method
   server.setMulticastTTL(255);
});
 
// Client sending message to server
client.send("Hello", 0, 7,
    1234, "localhost");

使用以下命令运行 index.js 文件：

node index.js

输出：

server listening 0.0.0.0:1234
UDP String: Hello

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