概述
因公司业务需要使用到指定源组播。经过一番测试，完成了相关功能的小Demo，废话不多说，直接上代码。
开发环境
操作系统：Windows
开发工具：IntelliJ IDEA
JDK：OpenJDK 19.0.1
运行环境
操作系统：中标麒麟V5U2
JDK：java-11-openjdk-devel
发送端
import java.io.IOException;
import java.net.*;
public class MulticastSender {
private static void usage() {
System.out.println("Usage: java MulticastSender.java address port text");
}
public static void main(String[] args) throws IOException, InterruptedException {
String host = "",text = "";
int port = -1;
if(args.length < 3) {
usage();
return ;
}else{
host = args[0];
port = Integer.parseInt(args[1]);
}
String[] parts = host.split("\\.");
if(parts.length != 4) {
System.out.println("非法地址格式，请重新输入");
return ;
}else{
int f = Integer.parseInt(parts[0]);
if(f < 224 || f > 239) {
System.out.println("非组播地址格式，请重新输入");
return ;
}
}
if(port <=0 || port > 65535) {
System.out.println("非法端口数值，请重新输入");
return ;
}
text = args[2];
if(text.isEmpty()) {
System.out.println("请输入需要发送的内容");
return;
}
MulticastSocket socket = new MulticastSocket();
InetSocketAddress isa = new InetSocketAddress(InetAddress.getByName(host), port);
NetworkInterface ni = NetworkInterface.getByInetAddress(InetAddress.getByName("192.168.1.4"));
socket.joinGroup(isa, null);
socket.setTimeToLive(5);
DatagramPacket dp = new DatagramPacket(text.getBytes(),text.length(), isa);
while(true) {
System.out.println("Sending Data...");
socket.send(dp);
Thread.sleep(1000);
}
}
}
接收端
import java.io.IOException;
import java.net.*;
import java.nio.ByteBuffer;
import java.nio.channels.DatagramChannel;
import java.nio.channels.MembershipKey;
import java.nio.channels.MulticastChannel;
/**
* 该程序在Linux平台下测试通过，但是Windows收不到Linux发出的数据
*/
public class SpecialMulticastReceiver {
private static void usage() {
System.out.println("Usage: java SpecialMulticastReceiver.java address port");
}
public static void main(String[] args) throws IOException, InterruptedException {
String host = "";
int port = -1;
ByteBuffer buffer = ByteBuffer.allocate(1024);
//byte buffer[] = new byte[1024];
if(args.length < 2) {
usage();
return ;
}else{
host = args[0];
port = Integer.parseInt(args[1]);
}
String[] parts = host.split("\\.");
if(parts.length != 4) {
System.out.println("非法地址格式，请重新输入");
return ;
}else{
int f = Integer.parseInt(parts[0]);
if(f < 224 || f > 239) {
System.out.println("非组播地址格式，请重新输入");
return ;
}
}
if(port <=0 || port > 65535) {
System.out.println("非法端口数值，请重新输入");
return ;
}
InetSocketAddress isa = new InetSocketAddress(port);
NetworkInterface ni = NetworkInterface.getByInetAddress(InetAddress.getByName("192.168.1.4"));
DatagramChannel dc = DatagramChannel.open(StandardProtocolFamily.INET)
.setOption(StandardSocketOptions.SO_REUSEADDR, true)
.setOption(StandardSocketOptions.IP_MULTICAST_LOOP, false)
.bind(isa)
.setOption(StandardSocketOptions.IP_MULTICAST_IF, ni);
//添加指定源
MembershipKey key = dc.join(InetAddress.getByName(host), ni, InetAddress.getByName("192.168.1.4"));
MembershipKey key1 = dc.join(InetAddress.getByName(host), ni, InetAddress.getByName("192.168.1.5"));
MulticastChannel mc = key.channel();
while(true) {
//接收数据
while((((DatagramChannel)mc).receive(buffer))!= null) {
buffer.flip();
System.out.println("Data: " + new String(buffer.array()));
buffer.clear();
}
}
}
}
问题&回答
Q: 接收端的代码在Windows平台死活收不到数据，不知道什么情况。但是在Linux平台则一切正常，有知道的小伙伴，希望解答一下哈。
A：
Q：在中标麒麟下添加指定源地址，当数量达到10个就会出现添加失败的情况。
A：修改net.ipv4.igmp_max_msf属性，其他linux内核应该也能通用。
修改代码如下：
echo "net.ipv4.igmp_max_msf=128" >> /etc/sysctl.conf
sysctl -p