由一个项目看java TCP/IP Socket编程

前一段时间刚做了个java程序和网络上多台机器的c程序通讯的项目，遵循的是TCP/IP协议，用到了java的Socket编程。网络通讯是java的强项，用TCP/IP协议可以方便的和网络上的其他程序互通消息。 

先来介绍下网络协议： 
    TCP/IP 
        Transmission Control Protocol 传输控制协议 
        Internet Protocol 互联网协议 
    UDP 
        User Datagram Protocol 用户数据协议 

连接协议： 
    分为： 
    面向连接协议: Connection Oriented Protocol 
    非连接协议: Connectionless Protocol 

    1).面向连接协议是指两台电脑在传输数据前，先会建立一个专属的连接。就如电信局的交换机会为打电话双方提供专属连接一样。 
    Internet上的面向连接协议就是TCP/IP 
    特点：确认回应；分组序号；流量控制。 
    TCP/IP属于可靠性传输，适合不容许有传输错误的网络程序设计使用 

    2).非连接协议：无专属连接，无分组，容错，距离短，可同时对多台电脑进行数据传输 
    Internet上的非连接协议就是UDP 

    TCP在网络通信上有极强的生命力，例如远程连接（Telnet）和文件传输（FTP）都需要不定长度的数据被可靠地传输。相比之下UDP操作简单，而且仅需要较少的监护，因此通常用于局域网高可靠性的分散系统中client/server应用程序。 


Socket 是程序与网络间的一种接口，大部分网络应用程序都是点对点的，所谓点就是服务器端和客户端所执行的程序。Socket是用来接收和传送分组的一个端点。 

java的Socket编程要用到java.net包，最常用的是net包下的6个类：InetAddress(互联网协议 (IP) 地址)类，Socket(套接字)类，ServerSocket(套接字服务器)类，DatagramSocket(发送和接收数据报包的套接字)类，DatagramPacket(数据报包)类，MulticastSocket(多播数据报套接字类用于发送和接收 IP 多播包)类，其中InetAddress、Socket、ServerSocket类是属于TCP面向连接协议，DatagramSocket、DatagramPacket和MulticastSocket类则属于UDP非连接协议的传送类。 

本项目因为使用TCP/IP协议，主要用到Socket和ServerSocket类 

项目代码如下 

package com.sse.monitor.serv;

import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.BufferedOutputStream;

import java.net.Socket;
import java.net.UnknownHostException;
import java.util.ArrayList;

import com.sse.monitor.bean.Message;
import com.sse.monitor.bean.MessageHead;
import com.sse.monitor.bean.ResponseMessage;
import com.sse.monitor.form.ListenerInvoke;
import com.sse.monitor.form.MainForm;
import com.sse.monitor.util.SwingUtils;

/**
 * Socket套接字工厂，对外接口是静态方法 SocketFactory.request(String, String, String, int)
 * Copyright: Copyright (c) 2008
 * Company: conserv
 * @author cuishen
 * @version 1.3
 */
public class SocketFactory {
    private Socket socket = null;
    private String targetIpAddress = null;
    private int targetPort = 0;
    private static SocketFactory sf = new SocketFactory();

    public SocketFactory() {
    }

    /**
     * 建立一条TCP/IP连接
     * @param targetIpAddress String 目标ip地址
     * @param targetPort String 目标端口
     * @throws IOException
     */
    private void connect(String targetIpAddress, int targetPort) throws IOException {
        setTargetIpAddress(targetIpAddress);
        setTargetPort(targetPort);
        if(socket == null)
            socket = new Socket(targetIpAddress, targetPort);
    }

    /**
     * 这是对外接口。发送命令，接收反馈和接收message放两个线程，
     * 发送命令并接收反馈是短连接，所以每次执行成功后，将销毁socket并终止线程，
     * 接收message是长连接，所以可能会new出n个线程，建议对接收message的线程做缓存
     * @param commandType String 命令类型
     * @param commandContent String 命令内容
     * @param targetIP String 目标ip
     * @param targetPort int 目标端口
     */
    public static void request(String commandType, String commandContent, String targetIP, int targetPort) {
        if (commandType.equalsIgnoreCase(MessageFactory.SCAN_COMMAND)) {
            sf.new GetMessageSocketThread(commandType, commandContent, targetIP, targetPort);
        } else {
            sf.new RequestSocketThread(commandType, commandContent, targetIP, targetPort);
        }
    }

    /**
     * 发送请求
     * @param commandType String 命令类型
     * @param commandContent String 命令内容
     * @param targetIp String 目标ip
     */
    private void sendRequest(String commandType, String commandContent, String targetIp) {
        OutputStream os = null;
        BufferedOutputStream bs = null;
        try {
            os = socket.getOutputStream();
            bs = new BufferedOutputStream(os);
            char[] message = MessageFactory.makeRequestMessage(targetIp, commandType, commandContent, MessageFactory.COMMAND_TRADE_CODE, MessageFactory.RIGHT_COMMAND, MessageFactory.MESSAGE_END_FLAG);
            for (int i = 0; i < message.length; i++)
                bs.write(new String(message).getBytes(), i, 1);
            bs.flush();
            SwingUtils.appendLog(MainForm.jTextArea, "发送请求：'" + commandType + "' '" + commandContent + "' '" + targetIp + "'", ReadConfig.commandStateShowLineCount);
        } catch (IOException e) {
            SwingUtils.appendLog(MainForm.jTextArea, "Error!!! 发送请求：'" + commandType + "' '" + commandContent + "' '" + targetIp + "'失败！！ " + e.getMessage(), ReadConfig.commandStateShowLineCount);
            e.printStackTrace();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
        }
    }

    /**
     * 获得反馈
     *
     * @return 如果成功获得反馈，则返回true；否则返回false
     */
    private boolean getResponse() {
        InputStream is = null;
        DataInputStream di = null;
        boolean returnFlag = false;
        try {
            is = socket.getInputStream();
            di = new DataInputStream(is);
            byte[] temp = new byte[1];
            int flag = 0;
            ArrayList tempByteList = new ArrayList();
            int i = 0;
            while (flag != -1) {
                i++;
                flag = di.read(temp = new byte[1]);
                if (flag != -1)
                    tempByteList.add(temp);
                if (i == 38)
                    break;
            }
            if (i == 1) {
                SwingUtils.Error("未收到response!!!");
                return false;
            }
            MessageHead messageHead = MessageFactory.readHead(tempByteList);

            SwingUtils.appendLog(MainForm.jTextArea, "收到 response", ReadConfig.commandStateShowLineCount);

            tempByteList = new ArrayList();
            i = 0;
            while (flag != -1) {
                i++;
                flag = di.read(temp = new byte[1]);
                if (flag != -1)
                    tempByteList.add(temp);
                if (i == 26)
                    break;
            }
            byte[] length = new byte[4];
            di.read(length);
            int len = Integer.parseInt(new String(length, MessageFactory.DEFAULT_CHAR_SET).trim());
            flag = 0;
            for (int j = 0; j < (len + 37); j++) {
                flag = di.read(temp = new byte[1]);
                if (flag == -1)
                    break;
                tempByteList.add(temp);
            }

            ResponseMessage rm = MessageFactory.readResponseMessage(tempByteList, len);

            if (messageHead.getErrorCode().equals(MessageFactory.SUCCESS))
                returnFlag = true;
            else
                SwingUtils.Error("errorCode: " + messageHead.getErrorCode() + "; content: " + rm.getCommandContent());
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
        }
        return returnFlag;
    }

    /**
     * 分发消息的方法,将消息按进程名发送到对应的消息缓存
     *
     * 消息缓存ListenerInvoke.messageMap，key = machineName +
     * '|' + programName + '|' + processId, value = messageList
     * 存放messageMap里面的键名的List -- ListenerInvoke.messageMapKeyList
     * 进程状态缓存ListenerInvoke.processStateMap, key = machineName + '|' +
     * programName + '|' + processId, value = String
     *
     * @param message Message
     */
    private void distributeMess(Message message) {
        String machineName = message.getMachineName();
        String programName = message.getProgramName();
        String processId = message.getProcessId();
        String content = message.getContent();
        String key = machineName + '|' + programName + '|' + processId;
        key = key.trim();
        ArrayList messageList = null;
        if (ListenerInvoke.messageMap.get(key) == null) {
            synchronized (ListenerInvoke.messageMap) {
                if (ListenerInvoke.messageMap.get(key) == null) {
                    messageList = new ArrayList();
                    messageList.add(content);
                    ListenerInvoke.messageMap.put(key, messageList);
                }
            }
        } else {
            messageList = (ArrayList) ListenerInvoke.messageMap.get(key);
            synchronized (messageList) {
                if (ListenerInvoke.messageMap.get(key) != null) {
                    messageList.add(content);
                    if (!ReadConfig.threadDeleteMessCacheOrFIFO
                            && messageList.size() >= ReadConfig.messageCacheSizeLimit)
                        messageList.remove(0);
                }
            }
        }
        if (!ListenerInvoke.messageMapKeyList.contains(key)) {
            synchronized (ListenerInvoke.messageMapKeyList) {
                if (!ListenerInvoke.messageMapKeyList.contains(key))
                    ListenerInvoke.messageMapKeyList.add(key);
            }
        }
    }

    /**
     * 接收message
     * @return Message
     */
    private boolean getMessage() {
        InputStream is = null;
        DataInputStream di = null;
        Message message = null;
        try {
            if (this.socket == null)  return false;
            is = this.socket.getInputStream();
            if (is == null)  return false;
            di = new DataInputStream(is);
            byte[] temp = new byte[1];
            int flag = 0;
            ArrayList tempByteList = new ArrayList();
            int i = 0;
            while (flag != -1) {
                i++;
                flag = di.read(temp = new byte[1]);
                if (flag != -1)
                    tempByteList.add(temp);
                if (i == 38)
                    break;
            }
            if (i == 1)  return false;

            tempByteList = new ArrayList();
            i = 0;
            while (flag != -1) {
                i++;
                flag = di.read(temp = new byte[1]);
                if (flag != -1)
                    tempByteList.add(temp);
                if (i == 74)
                    break;
            }
            byte[] length = new byte[4];
            di.read(length);
            int len = Integer.parseInt(new String(length,
                    MessageFactory.DEFAULT_CHAR_SET).trim());
            flag = 0;
            for (int j = 0; j < len; j++) {
                flag = di.read(temp = new byte[1]);
                if (flag == -1)
                    break;
                tempByteList.add(temp);
            }
            message = MessageFactory.readMessage(tempByteList, len);
            SwingUtils.appendLog(MainForm.jTextArea, "收到新 Message",
                    ReadConfig.commandStateShowLineCount);
            distributeMess(message);// 分发message
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
        }
        return true;
    }

    /**
     * 负责发送请求接收反馈的内部线程类，每new一个RequestSocketThread线程，
     * 就new一个socket，建立一条专属连接，成功接收反馈后将销毁socket，终止线程。
     * 将发送请求，接收反馈放进内部线程处理，是为了防止套接字阻塞造成主线程挂死。
     * @author cuishen
     * @version 1.2
     */
    class RequestSocketThread implements Runnable {
        private SocketFactory socketFactory;
        private String commandType = null;
        private String commandContent = null;
        private String targetIP = null;
        Thread t;

        public RequestSocketThread(String commandType, String commandContent, String targetIP, int targetPort) {
            this.socketFactory = new SocketFactory();
            try {
                this.socketFactory.connect(ReadConfig.targetIpAddress, ReadConfig.targetPort);
            } catch (UnknownHostException e) {
                SwingUtils.Error("主机 IP 地址无法确定,无法建立连接！ targetIP=" + ReadConfig.targetIpAddress + ", targetPort=" + ReadConfig.targetPort);
                e.printStackTrace();
            } catch (IOException e) {
                SwingUtils.Error("访问被拒绝，无法建立连接，请检查网络！ targetIP=" + ReadConfig.targetIpAddress + ", targetPort=" + ReadConfig.targetPort);
                e.printStackTrace();
            }
            this.commandType = commandType;
            this.commandContent = commandContent;
            this.targetIP = targetIP;
            t = new Thread(this);
            t.start();
        }

        public void run() {
            this.socketFactory.sendRequest(commandType, commandContent, targetIP);
            this.socketFactory.getResponse();
            stopThread();
        }

        public void stopThread() {
            try {
                this.commandType = null;
                this.commandContent = null;
                this.targetIP = null;
                socketFactory.closeSocket();
                socketFactory = null;
                this.t.join(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                t = null;
            }
        }
    }

    /**
     * 负责接收message的内部线程类，每new一个GetMessageSocketThread线程，
     * 就new一个socket，建立一条专属TCP/IP连接，getMessage是长连接，所以建议
     * 将该线程放入缓存方便管理
     * @author cuishen
     * @version 1.2
     */
    class GetMessageSocketThread implements Runnable {
        private SocketFactory socketFactory;
        private String commandType = null;
        private String commandContent = null;
        private String targetIP = null;
        Thread t;
        private boolean flag = false;
        private boolean ifGetResponse = true;
        private boolean ifGetMessage = true;
        private boolean ifSendRequest = true;
        private boolean ifCycle = true;

        public GetMessageSocketThread(String commandType, String commandContent, String targetIP, int targetPort) {

            this.socketFactory = new SocketFactory();
            try {
                this.socketFactory.connect(ReadConfig.targetIpAddress, ReadConfig.targetPort);
            } catch (UnknownHostException e) {
                SwingUtils.Error("主机 IP 地址无法确定,无法建立连接！ targetIP="
                        + ReadConfig.targetIpAddress + ", targetPort="
                        + ReadConfig.targetPort);
                e.printStackTrace();
            } catch (IOException e) {
                SwingUtils.Error("访问被拒绝，无法建立连接，请检查网络！ targetIP="
                        + ReadConfig.targetIpAddress + ", targetPort="
                        + ReadConfig.targetPort);
                e.printStackTrace();
            }
            this.commandType = commandType;
            this.commandContent = commandContent;
            this.targetIP = targetIP;
            t = new Thread(this);
            t.start();
        }

        public void run() {
            while (ifCycle) {
                if (ifSendRequest) {
                    this.socketFactory.sendRequest(commandType, commandContent, targetIP);
                    ifSendRequest = false;
                }
                if (ifGetResponse) {
                    flag = socketFactory.getResponse();
                    ifGetResponse = false;
                }
                if (flag && ifGetMessage && socketFactory.socket != null) {
                    if (!socketFactory.getMessage()) {
                        try {
                            Thread.sleep(ReadConfig.getMessageThreadSleep);
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }
                    }
                }
            }
        }

        public void stopThread() {
            try {
                this.commandType = null;
                this.commandContent = null;
                this.targetIP = null;
                ifGetMessage = false;
                ifCycle = false;
                socketFactory.closeSocket();
                socketFactory = null;
                this.t.join(100);
            } catch (InterruptedException e) {
                e.printStackTrace();
            } finally {
                t = null;
            }
        }
    }

    /**
     * 关闭套接字
     */
    private void closeSocket() {
        try {
            if (!socket.isClosed())
                socket.close();
            socket = null;
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    /**
     * @return the targetIpAddress
     */
    public String getTargetIpAddress() {
        return targetIpAddress;
    }

    /**
     * @param targetIpAddress
     *            the targetIpAddress to set
     */
    public void setTargetIpAddress(String targetIpAddress) {
        this.targetIpAddress = targetIpAddress;
    }

    /**
     * @return the targetPort
     */
    public int getTargetPort() {
        return targetPort;
    }

    /**
     * @param targetPort
     *            the targetPort to set
     */
    public void setTargetPort(int targetPort) {
        this.targetPort = targetPort;
    }

}

以上是Socket编程，ServerSocket在项目里没有用到，但是我也写了个包装类供参考 

package com.sse.monitor.serv;

import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

/**
 * 服务器套接字工厂
 * Copyright: Copyright (c) 2008
 * @author cuishen
 * @version 1.0
 */
public class ServerSocketFactory {
    private static ServerSocket server;
    private static Socket client;
    private boolean ifRunServer = true;

    public void runServer(int port) throws IOException {
        //本地建立一个套接字服务器，等待其他机器访问
        server = new ServerSocket(port);
        System.out.println("Socket Server Start...");
        new ServerThread();
    }


    class ServerThread implements Runnable {
        Thread t;

        public ServerThread() {
            t = new Thread(this);
            t.start();
        }

        public void run() {
            try {
                while(ifRunServer) {
                    if(client == null) client = server.accept();
                    if(client != null) //getMessage();
                    Thread.sleep(ReadConfig.serverThreadSleep);
                }
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
            catch (IOException e) {
                e.printStackTrace();
            }
        }
        public void stopThread() {
            try {
                ifRunServer = false;
                this.t.join(100);
            } catch (InterruptedException ex) {
                System.out.println("socket服务器线程终止异常！！！");
            } finally {
                t = null;
            }
        }
    }
}

Socket编程就是运用Socket或者ServerSocket类搭配线程来使用(由于TCP/IP属于可靠性传输，不会丢包)。可能会因为在发送请求或者接受消息时Socket阻塞而导致主线程挂死，因此发送请求、接收消息的方法要放进子线程里处理；对于同一目标ip和端口，在同一个子线程里只能new一个Socket，也就是说，要对同一地址建立多条连接，就要开启多个线程。而且注意连接可能会因作用不同分长连接和短连接，要分别处理，本项目中发送请求和接受message就分别属于短连接和长连接，因此分别开发了RequestSocketThread和GetMessageSocketThread两个子线程区分对待。可以同时开发个Message类来封装打包和解包消息的方法(项目中开发MessageFactory.java)，方便调用