网络编程--TCP

一. 简介

• 需要建立连接，形成传输数据的通道
• 通过三次握手完成连接，是可靠协议
• 以字节流的方式发送大量数据

二. 通信过程

客户端：
1..创建客户端的socket服务，指定目的主机和端口
2..为了发送数据，应该获取socket中的输出流
3..获取socket中的输入流来获取服务端的反馈数据
4..关闭资源

服务端：
1..创建服务端的ServerSocket服务，并监听一个端口
2..通过accept方法 等待并获取连接过来的客户端socket对象
3..获取客户端发送过来的数据（使用客户端socket的输入流来读取数据）
4..反馈数据到该客户端（使用客户端socket的输出流来写出数据）
5..关闭资源

三. 应用

1..客户端并发登录，服务端处理并反馈

/**   客户端*/class Client{    public static void main(String[] args) throws Exception {        Socket s = new Socket(InetAddress.getLocalHost(),10000);   //客户端建立socket服务，指定目的主机和端口        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));  //源-读取键盘录入        PrintWriter out = new PrintWriter(s.getOutputStream(),true);   //目的-socket输出流，包装成打印流        BufferedReader bin = new BufferedReader(new InputStreamReader(s.getInputStream()));  //源-读取socket输入流        int i =0;        for(i =0 ;i<3 ;i++)        {            String line = br.readLine();  //键盘录入的信息            if(line==null)                break;            out.println(line);     //写入socket输出流            String mess = bin.readLine();  //服务器反馈的信息            if(mess.contains("欢迎"))            {                System.out.println("Server Message:"+mess);                break;            }            System.out.println("Server Message:"+mess);        }        if(i>=3)            System.out.println("错误次数太多");        s.close();        br.close();    }}

/**服务端*/class Server {    public static void main(String[] args) throws Exception {        ServerSocket ss = new ServerSocket(10000);  //服务端建立ServerSocket服务，监听指定端口        while(true)        {            Socket s = ss.accept();            new Thread(new ServerThread(s)).start();  //进来一个用户，则开启一个线程        }    }}class ServerThread implements Runnable{    private Socket s;    ServerThread(Socket s){        this.s = s;    }    public void run() {        String ip = s.getInetAddress().getHostAddress();        System.out.println(ip+"已连接");        try{            for(int i =0 ;i<3;i++)            {                BufferedReader bfr = new BufferedReader(new FileReader("E:\\user.txt")); //源-服务端数据文件或数据库,包装成BufferedReader                BufferedReader bin = new BufferedReader(new InputStreamReader(s.getInputStream())); //源-客户端提交的数据                PrintWriter out = new PrintWriter(s.getOutputStream(),true);  //目的-socket输出流，包装成打印流                String name = bin.readLine();                String line = null;                boolean flag = false;                while((line = bfr.readLine())!=null)                {                    if(line.equals(name))                    {                        flag = true;                        break;                    }                }                if(flag == true)                {                    System.out.println(name+"已登录");                    out.println("欢迎"+name);   //将信息反馈给客户端                }                else                    out.println("用户名不存在");            }            s.close();        }catch(Exception e){            throw new RuntimeException(ip+"校验失败");        }    }}

2..客户端并发上传图片，服务端接收并反馈

/**  客户端*/class UploadClient {    public static void main(String[] args) throws Exception {        Socket s = new Socket(InetAddress.getLocalHost(),9999);        BufferedOutputStream bout = new BufferedOutputStream(s.getOutputStream()); //目的-socket输出流        FileInputStream fin = new FileInputStream("E:\\晴天.mp3");  //读文件并写入socket输出流        int len = 0;        while((len = fin.read())!=-1)        {            bout.write(len);        }        s.shutdownOutput();  //写完..结束标记        BufferedReader bin = new BufferedReader(new InputStreamReader(s.getInputStream()));  //源-读取socket输入流        String mess = bin.readLine();  //服务器反馈的信息        System.out.println(mess);        s.close();        fin.close();    }}

/**    服务端* /class UploadServer{    public static void main(String[] args) throws Exception {        ServerSocket ss = new ServerSocket(9999);        while(true)        {            Socket s = ss.accept();            new Thread(new UploadThread(s)).start();        }    }}class UploadThread implements Runnable {    private Socket s = null;    UploadThread(Socket s)    {        this.s = s;    }    public void run(){        String ip = s.getInetAddress().getHostAddress();        try {            System.out.println(ip+"已连接");            int time = (int) System.currentTimeMillis();            BufferedInputStream bin = new BufferedInputStream(s.getInputStream()); //源-socket输入流，客户端发来的数据            FileOutputStream fi = new FileOutputStream("F:\\"+time+".mp3");  //目的-磁盘，将客户端发来的文件写入本地            int len;            while((len=bin.read())!=-1)            {                fi.write(len);            }            PrintWriter out = new PrintWriter(s.getOutputStream(),true);  //目的-socket输出流，包装成打印流            out.println("上传成功");  //反馈给客户端            fi.close();            s.close();        } catch (Exception e) {            throw new RuntimeException(ip+"上传失败");        }    }}