Android开发：长连接通信设计与实现

一.前言

Android长连接应用于服务器需要主动通知客户端的一些场景，例如推送消息和即时通讯。除了接入第三方SDK来实现外，在业务要求不是很高的情况下，完全可以自己编写一套实现方案。

二.正文

Android客户端长连接通信通过TCP协议的套接字（Socket）实现。下面通过对Socket的封装来实现长连接通信：

• ClientSocket：Socket创建、连接和数据传输；

• SocketInterface：Socket运行周期回调接口；

• ClientService：业务逻辑处理。

 （1）ClientSocket通过开启一个线程来进行Socket的创建和连接，连接成功后，等待服务器信息，并按照text协议（以“\n”结尾的字符串）来读取输入流。

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.InetSocketAddress;
import java.net.Socket;public class ClientSocket {//连接超时时间(ms)private int TIME_OUT = 3000;//远程ip地址private String host;//远程端口private int port;//socket对象private Socket socket;//输出流private BufferedWriter bufferedWriter;//输入流(text协议)private BufferedReader bufferedReader;//回调接口private SocketInterface socketInterface;//socket是否正常运行中private boolean isRunning = false;/*** 设置通信地址** @param host 主机ip* @param port 端口*/public void setAddress(String host, int port) {this.host = host;this.port = port;}/*** 开启(子线程)*/public void start() {new Thread(this::connect).start();}/*** 开始连接*/private void connect() {//连接try {this.socket = new Socket();this.socket.connect(new InetSocketAddress(this.host, this.port), this.TIME_OUT);this.socketInterface.onConnect();OutputStreamWriter outputStreamWriter = new OutputStreamWriter(this.socket.getOutputStream());this.bufferedWriter = new BufferedWriter(outputStreamWriter);InputStreamReader inputStreamReader = new InputStreamReader(this.socket.getInputStream());this.bufferedReader = new BufferedReader(inputStreamReader);this.isRunning = true;this.socketInterface.onReady();} catch (Exception e) {this.isRunning = false;this.socketInterface.onConnectFailure(e.getLocalizedMessage());return;}//接收数据try {while (isRunning) {String msg = bufferedReader.readLine();socketInterface.onMessage(msg);}} catch (Exception e) {isRunning = false;}//连接关闭socketInterface.onClose();}/*** 发送信息** @param msg 信息体*/synchronized public void send(String msg) {if (!this.isRunning) {return;}try {this.bufferedWriter.write(msg + "\n");this.bufferedWriter.flush();} catch (IOException e) {isRunning = false;}}/*** 关闭Socket连接*/public void close() {if (isRunning) {try {socket.close();isRunning = false;} catch (IOException ignored) {}}}/*** @return 当前Socket运行状态*/public boolean isRunning() {return this.isRunning;}/*** 设置Socket运行周期回调*/public void setSocketInterface(SocketInterface socketInterface) {this.socketInterface = socketInterface;}
}

（2） SocketInterface 声明了简单接口，可按照实际情况来更改。

public interface SocketInterface {void onConnect();void onConnectFailure(String error);void onReady();void onMessage(String msg);void onClose();}

 （3）ClientService 采用单例模式，只进行一个Socket通信，通过设置回调来进行逻辑处理。

public class ClientService {static ClientSocket clientSocket;static SocketInterface socketInterface;static {clientSocket = new ClientSocket();initSocketInterface();}/*** 开启通信服务** @param host 主机ip* @param port 端口*/static public void startService(String host, int port) {if (clientSocket.isRunning()) {return;}clientSocket.setAddress(host, port);clientSocket.setSocketInterface(socketInterface);clientSocket.start();}/*** 发送信息*/static public void sendMessage(String msg) {if (clientSocket.isRunning()) {clientSocket.send(msg);}}/*** 关闭通信服务*/static public void closeService() {clientSocket.close();}/*** 初始化回调*/static private void initSocketInterface() {socketInterface = new SocketInterface() {@Overridepublic void onConnect() {//成功连接LogUtil.log("onConnect");}@Overridepublic void onConnectFailure(String error) {//连接失败，可根据错误类型进行相应处理，如重连LogUtil.log("onConnectFailure:" + error);}@Overridepublic void onReady() {//已准备完毕，可进行发送信息，开启心跳线程等LogUtil.log("onReady");}@Overridepublic void onMessage(String msg) {//服务器信息到达，进行业务处理LogUtil.log("onMessage:" + msg);}@Overridepublic void onClose() {//连接关闭，此处可进行重连或清理操作LogUtil.log("onClose");}};}
}

在需要开启时候传入服务器ip和端口即可。 

//开启服务
ClientService.startService("192.168.1.102", 8080);

 这只是Android长连接通信的一个基本实现，实际情况还要考虑通信数据协议和通信保活问题。

三.结语

本文基于自身知识经验编写，只供参考学习，不足之处还请指正，欢迎伙伴们来一起探讨交流！

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