1.目標(biāo)
解碼服務(wù)器消息中的[消息有效內(nèi)容]，有效內(nèi)容首尾是固定的分隔符$OUTSTA和#，內(nèi)容格式如下：
$OUTSTA[消息有效內(nèi)容]#[結(jié)束內(nèi)容，可能為有效內(nèi)容]
2.pom.xml
添加netty依賴
<dependency>
<groupId>io.netty</groupId>
<artifactId>netty-all</artifactId>
<version>4.1.14.Final</version>
</dependency>
3.TcpClient.java
package com.airkisser.netty;
import io.netty.bootstrap.Bootstrap;
import io.netty.buffer.ByteBuf;
import io.netty.buffer.Unpooled;
import io.netty.channel.*;
import io.netty.channel.nio.NioEventLoopGroup;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.socket.nio.NioSocketChannel;
import io.netty.handler.codec.DelimiterBasedFrameDecoder;
import io.netty.handler.codec.string.StringDecoder;
import io.netty.handler.logging.LogLevel;
import io.netty.handler.logging.LoggingHandler;
/**
* TCP/IP客戶端
*/
public class TcpClient {
/**
* 連接TCP服務(wù)端
* @param host 服務(wù)端IP
* @param port 服務(wù)端監(jiān)聽(tīng)端口號(hào)
*/
public void connect(String host, int port) {
// 配置NIO線程組
EventLoopGroup group = new NioEventLoopGroup();
Bootstrap b = new Bootstrap();
b.group(group).channel(NioSocketChannel.class)
.option(ChannelOption.TCP_NODELAY, true)
.handler(new LoggingHandler(LogLevel.DEBUG))
.handler(new ChannelInitializer<SocketChannel>() {
protected void initChannel(SocketChannel socketChannel) throws Exception {
ByteBuf startDelimiter = Unpooled.copiedBuffer("$OUTSTA".getBytes());
ByteBuf endDelimiter = Unpooled.copiedBuffer("#".getBytes());
socketChannel.pipeline()
/* 分隔符解碼器
如果接收內(nèi)容超過(guò)2048的長(zhǎng)度還沒(méi)有查找到分隔符，拋出TooLongFrameException異常，防止內(nèi)存溢出
可以定義一個(gè)或多個(gè)分隔符，解碼器將只取分隔符之間的內(nèi)容
例如：
服務(wù)端一次返回消息內(nèi)容為：
$OUTSTA65535,10,1256,170823_162540,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0#ss
則定義兩個(gè)分隔符"$OUTSTA"和"#ss"
那么第一次接收服務(wù)器返回消息時(shí)解碼后內(nèi)容為一條：
65535,10,1256,170823_162540,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0
還剩下'#ss'后面的內(nèi)容沒(méi)有被解碼，等待接收下一條服務(wù)器消息
第二次接收服務(wù)器返回消息時(shí)解碼后的內(nèi)容為兩條：
第一條：空字符串""
第二條：
65535,10,1256,170823_162540,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0
需要注意的是："#ss"和"$OUTSTA"作為分隔的首尾，中間的內(nèi)容被解碼為空字符串
需要對(duì)解碼后的內(nèi)容進(jìn)行空字符串過(guò)濾
如果定義兩個(gè)分隔符為"$OUTSTA"和"#"
那么第一次接收服務(wù)器返回消息時(shí)解碼后內(nèi)容為一條：
65535,10,1256,170823_162540,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0
還剩下'#'后面的內(nèi)容沒(méi)有被解碼，等待接收下一條服務(wù)器消息
第二次接收服務(wù)器返回消息時(shí)解碼后的內(nèi)容為兩條：
第一條：ss
第二條：
65535,10,1256,170823_162540,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0
其中第一條'ss'是第一次接收到的服務(wù)器消息'#'后面的內(nèi)容以及第二次接收到的服務(wù)器消息'$OUTSTA'之前的內(nèi)容
是我們不需要的內(nèi)容，可以通過(guò)限定長(zhǎng)度過(guò)濾掉，不對(duì)該條消息做處理
同理，還剩下'#'后面的內(nèi)容沒(méi)有被解碼，等待接收下一條服務(wù)器消息
*/
.addLast(new DelimiterBasedFrameDecoder(2048, startDelimiter, endDelimiter))
/*
* 將分隔符解碼后的內(nèi)容轉(zhuǎn)為字符串
*/
.addLast(new StringDecoder())
.addLast(new ChannelInboundHandlerAdapter() {
@Override
public void channelActive(ChannelHandlerContext ctx) throws Exception {
//@TODO 進(jìn)行連接成功后的操作
System.out.println("連接成功... ");
}
@Override
public void channelRead(ChannelHandlerContext ctx, Object msg) throws Exception {
// StringDecoder解碼后的信息,
String message = (String) msg;
// 前面已經(jīng)說(shuō)了，通過(guò)分隔符解碼后的消息中有一部分并不是我們需要的消息
// 此時(shí)我們可以通過(guò)一些限制條件過(guò)濾掉這些我們不需要的內(nèi)容，比如空字符串，此處通過(guò)限定長(zhǎng)度來(lái)過(guò)濾：長(zhǎng)度大于10，
// 可以根據(jù)實(shí)際情況進(jìn)行過(guò)濾
// 只對(duì)過(guò)濾后的內(nèi)容進(jìn)行解析
if (message != null && message.length() > 10) {
System.out.println("接收內(nèi)容：\n" + message);
// @TODO 對(duì)消息進(jìn)行解析等操作，一般放在線程或線程池中處理
}
}
@Override
public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) throws Exception {
// @TODO 捕捉到異常后進(jìn)行重連或者其他異常處理操作
System.out.println("發(fā)生異常...");
cause.printStackTrace();
ctx.channel().close();
}
});
}
});
try {
ChannelFuture f = b.connect(host, port).sync();
} catch (InterruptedException e) {
// @TODO 處理連接失敗后的異常
e.printStackTrace();
}
}
public static void main(String[] args) {
TcpClient client = new TcpClient();
client.connect("127.0.0.1", 12800);
}
}
4.測(cè)試
步驟1：?jiǎn)?dòng)TCP模擬服務(wù)端
監(jiān)聽(tīng)地址：127.0.0.1
監(jiān)聽(tīng)端口：12800
模擬消息：
$OUTSTA65535,10,1256,170823_162540,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0,0,0#ss
客戶端需要的有效內(nèi)容：
65535,10,1256,170823_162540,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0.0,0,0,0,0
image.png
步驟2：運(yùn)行TcpClient中的main方法作為客戶端
步驟3：服務(wù)端發(fā)送消息給客戶端，客戶端控制臺(tái)打印內(nèi)容如下:
image.png
解碼完成。
