通过netty实现服务端与客户端的长连接通讯，及心跳检测。
基本思路：netty服务端通过一个Map保存所有连接上来的客户端SocketChannel,客户端的Id作为Map的key。每次服务器端如果要向某个客户端发送消息，只需根据ClientId取出对应的SocketChannel,往里面写入message即可。心跳检测通过IdleEvent 事件，定时向服务端放送Ping消息，检测SocketChannel是否终断。
环境JDK1.8 和netty5
以下是具体的代码实现和介绍：
1公共的Share部分(主要包含消息协议类型的定义)
设计消息类型：
public enum MsgType {
PING,ASK,REPLY,LOGIN
}
Message基类：
//必须实现序列,serialVersionUID 一定要有,否者在netty消息序列化反序列化会有问题，接收不到消息！！！
public abstract class BaseMsg implements Serializable {
private static final long serialVersionUID = 1L;
private MsgType type;
//必须唯一，否者会出现channel调用混乱
private String clientId; //初始化客户端id
public BaseMsg() {
this.clientId = Constants.getClientId();
} public String getClientId() {
return clientId;
} public void setClientId(String clientId) {
this.clientId = clientId;
} public MsgType getType() {
return type;
} public void setType(MsgType type) {
this.type = type;
}
}
常量设置：
public class Constants {
private static String clientId;
public static String getClientId() {
return clientId;
}
public static void setClientId(String clientId) {
Constants.clientId = clientId;
}
}
登录类型消息：
public class LoginMsg extends BaseMsg {
private String userName;
private String password;
public LoginMsg() {
super();
setType(MsgType.LOGIN);
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
}
心跳检测Ping类型消息：
public class PingMsg extends BaseMsg {
public PingMsg() {
super();
setType(MsgType.PING);
}
}
请求类型消息：
public class AskMsg extends BaseMsg {
public AskMsg() {
super();
setType(MsgType.ASK);
}
private AskParams params;
public AskParams getParams() {
return params;
}
public void setParams(AskParams params) {
this.params = params;
}
}
//请求类型参数
//必须实现序列化接口
public class AskParams implements Serializable {
private static final long serialVersionUID = 1L;
private String auth;
public String getAuth() {
return auth;
}
public void setAuth(String auth) {
this.auth = auth;
}
}
响应类型消息：
public class ReplyMsg extends BaseMsg {
public ReplyMsg() {
super();
setType(MsgType.REPLY);
}
private ReplyBody body;
public ReplyBody getBody() {
return body;
}
public void setBody(ReplyBody body) {
this.body = body;
}
}
//相应类型body对像
public class ReplyBody implements Serializable {
private static final long serialVersionUID = 1L;
}
public class ReplyClientBody extends ReplyBody {
private String clientInfo;
public ReplyClientBody(String clientInfo) {
this.clientInfo = clientInfo;
}
public String getClientInfo() {
return clientInfo;
}
public void setClientInfo(String clientInfo) {
this.clientInfo = clientInfo;
}
}
public class ReplyServerBody extends ReplyBody {
private String serverInfo;
public ReplyServerBody(String serverInfo) {
this.serverInfo = serverInfo;
}
public String getServerInfo() {
return serverInfo;
}
public void setServerInfo(String serverInfo) {
this.serverInfo = serverInfo;
}
}
2 Server端：主要包含对SocketChannel引用的Map,ChannelHandler的实现和Bootstrap.
Map:
public class NettyChannelMap {
private static Map<String,SocketChannel> map=new ConcurrentHashMap<String, SocketChannel>();
public static void add(String clientId,SocketChannel socketChannel){
map.put(clientId,socketChannel);
}
public static Channel get(String clientId){
return map.get(clientId);
}
public static void remove(SocketChannel socketChannel){
for (Map.Entry entry:map.entrySet()){
if (entry.getValue()==socketChannel){
map.remove(entry.getKey());
}
}
}
}
Handler
public class NettyServerHandler extends SimpleChannelInboundHandler<BaseMsg> {
@Override
public void channelInactive(ChannelHandlerContext ctx) throws Exception {
//channel失效，从Map中移除
NettyChannelMap.remove((SocketChannel)ctx.channel());
}
@Override
protected void messageReceived(ChannelHandlerContext channelHandlerContext, BaseMsg baseMsg) throws Exception {
if(MsgType.LOGIN.equals(baseMsg.getType())){
LoginMsg loginMsg=(LoginMsg)baseMsg;
if("robin".equals(loginMsg.getUserName())&&"yao".equals(loginMsg.getPassword())){
//登录成功,把channel存到服务端的map中
NettyChannelMap.add(loginMsg.getClientId(),(SocketChannel)channelHandlerContext.channel());
System.out.println("client"+loginMsg.getClientId()+" 登录成功");
}
}else{
if(NettyChannelMap.get(baseMsg.getClientId())==null){
//说明未登录，或者连接断了，服务器向客户端发起登录请求，让客户端重新登录
LoginMsg loginMsg=new LoginMsg();
channelHandlerContext.channel().writeAndFlush(loginMsg);
}
}
switch (baseMsg.getType()){
case PING:{
PingMsg pingMsg=(PingMsg)baseMsg;
PingMsg replyPing=new PingMsg();
NettyChannelMap.get(pingMsg.getClientId()).writeAndFlush(replyPing);
}break;
case ASK:{
//收到客户端的请求
AskMsg askMsg=(AskMsg)baseMsg;
if("authToken".equals(askMsg.getParams().getAuth())){
ReplyServerBody replyBody=new ReplyServerBody("server info $$$$ !!!");
ReplyMsg replyMsg=new ReplyMsg();
replyMsg.setBody(replyBody);
NettyChannelMap.get(askMsg.getClientId()).writeAndFlush(replyMsg);
}
}break;
case REPLY:{
//收到客户端回复
ReplyMsg replyMsg=(ReplyMsg)baseMsg;
ReplyClientBody clientBody=(ReplyClientBody)replyMsg.getBody();
System.out.println("receive client msg: "+clientBody.getClientInfo());
}break;
default:break;
}
ReferenceCountUtil.release(baseMsg);
}
}
ServerBootstrap:
public class NettyServerBootstrap {
private int port;
private SocketChannel socketChannel;
public NettyServerBootstrap(int port) throws InterruptedException {
this.port = port;
bind();
}
private void bind() throws InterruptedException {
EventLoopGroup boss=new NioEventLoopGroup();
EventLoopGroup worker=new NioEventLoopGroup();
ServerBootstrap bootstrap=new ServerBootstrap();
bootstrap.group(boss,worker);
bootstrap.channel(NioServerSocketChannel.class);
bootstrap.option(ChannelOption.SO_BACKLOG, 128);
//通过NoDelay禁用Nagle,使消息立即发出去，不用等待到一定的数据量才发出去
bootstrap.option(ChannelOption.TCP_NODELAY, true);
//保持长连接状态
bootstrap.childOption(ChannelOption.SO_KEEPALIVE, true);
bootstrap.childHandler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel socketChannel) throws Exception {
ChannelPipeline p = socketChannel.pipeline();
p.addLast(new ObjectEncoder());
p.addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
p.addLast(new NettyServerHandler());
}
});
ChannelFuture f= bootstrap.bind(port).sync();
if(f.isSuccess()){
System.out.println("server start---------------");
}
}
public static void main(String []args) throws InterruptedException {
NettyServerBootstrap bootstrap=new NettyServerBootstrap(9999);
while (true){
SocketChannel channel=(SocketChannel)NettyChannelMap.get("001");
if(channel!=null){
AskMsg askMsg=new AskMsg();
channel.writeAndFlush(askMsg);
}
TimeUnit.SECONDS.sleep(5);
}
}
}
3 Client端：包含发起登录，发送心跳，及对应消息处理
handler
public class NettyClientHandler extends SimpleChannelInboundHandler<BaseMsg> {
//利用写空闲发送心跳检测消息
@Override
public void userEventTriggered(ChannelHandlerContext ctx, Object evt) throws Exception {
if (evt instanceof IdleStateEvent) {
IdleStateEvent e = (IdleStateEvent) evt;
switch (e.state()) {
case WRITER_IDLE:
PingMsg pingMsg=new PingMsg();
ctx.writeAndFlush(pingMsg);
System.out.println("send ping to server----------");
break;
default:
break;
}
}
}
@Override
protected void messageReceived(ChannelHandlerContext channelHandlerContext, BaseMsg baseMsg) throws Exception {
MsgType msgType=baseMsg.getType();
switch (msgType){
case LOGIN:{
//向服务器发起登录
LoginMsg loginMsg=new LoginMsg();
loginMsg.setPassword("yao");
loginMsg.setUserName("robin");
channelHandlerContext.writeAndFlush(loginMsg);
}break;
case PING:{
System.out.println("receive ping from server----------");
}break;
case ASK:{
ReplyClientBody replyClientBody=new ReplyClientBody("client info **** !!!");
ReplyMsg replyMsg=new ReplyMsg();
replyMsg.setBody(replyClientBody);
channelHandlerContext.writeAndFlush(replyMsg);
}break;
case REPLY:{
ReplyMsg replyMsg=(ReplyMsg)baseMsg;
ReplyServerBody replyServerBody=(ReplyServerBody)replyMsg.getBody();
System.out.println("receive client msg: "+replyServerBody.getServerInfo());
}
default:break;
}
ReferenceCountUtil.release(msgType);
}
}
bootstrap
public class NettyClientBootstrap {
private int port;
private String host;
private SocketChannel socketChannel;
private static final EventExecutorGroup group = new DefaultEventExecutorGroup(20);
public NettyClientBootstrap(int port, String host) throws InterruptedException {
this.port = port;
this.host = host;
start();
}
private void start() throws InterruptedException {
EventLoopGroup eventLoopGroup=new NioEventLoopGroup();
Bootstrap bootstrap=new Bootstrap();
bootstrap.channel(NioSocketChannel.class);
bootstrap.option(ChannelOption.SO_KEEPALIVE,true);
bootstrap.group(eventLoopGroup);
bootstrap.remoteAddress(host,port);
bootstrap.handler(new ChannelInitializer<SocketChannel>() {
@Override
protected void initChannel(SocketChannel socketChannel) throws Exception {
socketChannel.pipeline().addLast(new IdleStateHandler(20,10,0));
socketChannel.pipeline().addLast(new ObjectEncoder());
socketChannel.pipeline().addLast(new ObjectDecoder(ClassResolvers.cacheDisabled(null)));
socketChannel.pipeline().addLast(new NettyClientHandler());
}
});
ChannelFuture future =bootstrap.connect(host,port).sync();
if (future.isSuccess()) {
socketChannel = (SocketChannel)future.channel();
System.out.println("connect server 成功---------");
}
}
public static void main(String[]args) throws InterruptedException {
Constants.setClientId("001");
NettyClientBootstrap bootstrap=new NettyClientBootstrap(9999,"localhost");
LoginMsg loginMsg=new LoginMsg();
loginMsg.setPassword("yao");
loginMsg.setUserName("robin");
bootstrap.socketChannel.writeAndFlush(loginMsg);
while (true){
TimeUnit.SECONDS.sleep(3);
AskMsg askMsg=new AskMsg();
AskParams askParams=new AskParams();
askParams.setAuth("authToken");
askMsg.setParams(askParams);
bootstrap.socketChannel.writeAndFlush(askMsg);
}
}
}
具体的例子和相应pom.xml 见 https://github.com/WangErXiao/ServerClient