Add a DNS client example. (#10237)

Motivation:

It seems that there is no DNS client example in Netty project so far.

Modification:

Add a Netty DNS client example.

Result:

More examples
This commit is contained in:
feijermu 2020-05-07 16:46:41 +08:00 committed by GitHub
parent 4c9a30d5f9
commit 731d33070f
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2 changed files with 112 additions and 0 deletions

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@ -108,6 +108,11 @@
<artifactId>netty-codec-haproxy</artifactId> <artifactId>netty-codec-haproxy</artifactId>
<version>${project.version}</version> <version>${project.version}</version>
</dependency> </dependency>
<dependency>
<groupId>${project.groupId}</groupId>
<artifactId>netty-codec-dns</artifactId>
<version>${project.version}</version>
</dependency>
<dependency> <dependency>
<groupId>com.google.protobuf</groupId> <groupId>com.google.protobuf</groupId>

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@ -0,0 +1,107 @@
/*
* Copyright 2020 The Netty Project
*
* The Netty Project licenses this file to you under the Apache License,
* version 2.0 (the "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations
* under the License.
*/
package io.netty.example.dns.udp;
import java.net.InetSocketAddress;
import java.util.concurrent.TimeUnit;
import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBufUtil;
import io.netty.channel.Channel;
import io.netty.channel.ChannelHandlerContext;
import io.netty.channel.ChannelInitializer;
import io.netty.channel.ChannelPipeline;
import io.netty.channel.EventLoopGroup;
import io.netty.channel.SimpleChannelInboundHandler;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.DatagramChannel;
import io.netty.channel.socket.nio.NioDatagramChannel;
import io.netty.handler.codec.dns.DatagramDnsQuery;
import io.netty.handler.codec.dns.DatagramDnsQueryEncoder;
import io.netty.handler.codec.dns.DatagramDnsResponse;
import io.netty.handler.codec.dns.DatagramDnsResponseDecoder;
import io.netty.handler.codec.dns.DefaultDnsQuestion;
import io.netty.handler.codec.dns.DnsQuery;
import io.netty.handler.codec.dns.DnsQuestion;
import io.netty.handler.codec.dns.DnsRawRecord;
import io.netty.handler.codec.dns.DnsRecord;
import io.netty.handler.codec.dns.DnsRecordType;
import io.netty.handler.codec.dns.DnsSection;
import io.netty.util.NetUtil;
public final class DnsClient {
private static final String QUERY_DOMAIN = "www.example.com";
private static final int DNS_SERVER_PORT = 53;
private static final String DNS_SERVER_HOST = "8.8.8.8";
private DnsClient() { }
private static void handleQueryResp(DatagramDnsResponse msg) {
if (msg.count(DnsSection.QUESTION) > 0) {
DnsQuestion question = msg.recordAt(DnsSection.QUESTION, 0);
System.out.printf("name: %s%n", question.name());
}
for (int i = 0, count = msg.count(DnsSection.ANSWER); i < count; i++) {
DnsRecord record = msg.recordAt(DnsSection.ANSWER, i);
if (record.type() == DnsRecordType.A) {
//just print the IP after query
DnsRawRecord raw = (DnsRawRecord) record;
System.out.println(NetUtil.bytesToIpAddress(ByteBufUtil.getBytes(raw.content())));
}
}
}
public static void main(String[] args) throws Exception {
InetSocketAddress addr = new InetSocketAddress(DNS_SERVER_HOST, DNS_SERVER_PORT);
EventLoopGroup group = new NioEventLoopGroup();
try {
Bootstrap b = new Bootstrap();
b.group(group)
.channel(NioDatagramChannel.class)
.handler(new ChannelInitializer<DatagramChannel>() {
@Override
protected void initChannel(DatagramChannel ch) throws Exception {
ChannelPipeline p = ch.pipeline();
p.addLast(new DatagramDnsQueryEncoder())
.addLast(new DatagramDnsResponseDecoder())
.addLast(new SimpleChannelInboundHandler<DatagramDnsResponse>() {
@Override
protected void channelRead0(ChannelHandlerContext ctx, DatagramDnsResponse msg) {
try {
handleQueryResp(msg);
} finally {
ctx.close();
}
}
});
}
});
final Channel ch = b.bind(0).sync().channel();
DnsQuery query = new DatagramDnsQuery(null, addr, 1).setRecord(
DnsSection.QUESTION,
new DefaultDnsQuestion(QUERY_DOMAIN, DnsRecordType.A));
ch.writeAndFlush(query).sync();
boolean succ = ch.closeFuture().await(10, TimeUnit.SECONDS);
if (!succ) {
System.err.println("dns query timeout!");
ch.close().sync();
}
} finally {
group.shutdownGracefully();
}
}
}