Java简单实现UDP和TCP

TCP实现

TCP协议需要在双方之间建立连接，通过输入输出流来进行数据的交换，建立需要通过三次握手，断开需要四次挥手，保证了数据的完整性，但传输效率也会相应的降低。

简单的TCP实现

//服务端
public class TcpServer {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(8886);  // 建立服务端，ip为本机ip,端口为8886
        Socket accept = serverSocket.accept();  // 监听客户端的连接，一旦有客户端连接，则会返回客户端对应的accept
        InputStream in = accept.getInputStream();   //获取到客户端的输出流
        byte b[] = new byte[1024];
        int len = in.read(b);
        System.out.println("接受到客户端数据,返回数据"+new String(b,0,len));  
        OutputStream out = accept.getOutputStream();  // 给客户端发送消息
        out.write("服务端已经接受".getBytes());
        serverSocket.close();
    }
}
// 客户端
public class TcpClient {
    public static void main(String[] args) throws IOException {
        Socket socket = new Socket("127.0.0.1", 8886);   // 通过Socket来建立和服务端的连接
        OutputStream out = socket.getOutputStream();   // 获取输出流（客户端输出流即向服务端输出信息）
        out.write("hello tcp Server".getBytes());  // 输出信息
        InputStream in = socket.getInputStream();   // 接受服务端的消息
        byte b[] = new byte[1024];
        int len = in.read(b);
        System.out.println("接受到服务器消息 ： "+new String(b,0,len));   // 输出
        out.write("返回的的数据已经收到 ".getBytes());  // 向服务器返回消息
        socket.close();
    }
}

改进服务端，启用多线程来接受客户端的数据

// server
 public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(8886); // 建立服务端，ip为本机ip,端口为8886
        int i=4;
        while(i>2){
            Socket accept = serverSocket.accept(); // 监听客户端的连接，一旦有客户端连接，则会返回客户端对应的accept
            ServerThread st = new ServerThread(accept);   // 启动线程
            Thread th = new Thread(st);
            th.start();
        }
        serverSocket.close();
    }
// thread
public class ServerThread implements Runnable {
    private Socket accept;
    public ServerThread(Socket s) {
        this.accept = s;
    }
    public void run(){
        InputStream in;
        try {
            in = accept.getInputStream();
            byte b[] = new byte[1024];
            int len = in.read(b);
            System.out.println("接受到客户端数据,返回数据" + new String(b, 0, len));
            OutputStream out = accept.getOutputStream(); // 给客户端发送消息
            out.write("服务端已经接受".getBytes());
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

传递图片

// 服务端
public class Server {
    public static void main(String[] args) throws IOException {
        ServerSocket serverSocket = new ServerSocket(5555);
        Socket ss = serverSocket.accept();
        BufferedInputStream br = new BufferedInputStream(ss.getInputStream());
        BufferedOutputStream bw = new BufferedOutputStream(new FileOutputStream("copy.jpg"));  // 写出文件流
        byte b[] = new byte[1024];
        int len = 0;
        while ((len = br.read(b)) != -1) {   // 写出文件
            bw.write(b, 0, len);
            bw.flush();  // 别忘了刷新，要不然最后一块缓冲区字符串会缺失
        }
        BufferedWriter bw2 = new BufferedWriter(new OutputStreamWriter(ss.getOutputStream())); // 输出
        bw2.write("图片传输成功");
        bw2.flush();
        bw.close();
        ss.close();
    }
}
// 客户端
public class Client {
    public static void main(String[] args) throws UnknownHostException, IOException {
        Socket socket = new Socket("127.0.0.1", 5555);
        BufferedInputStream in = new BufferedInputStream(new FileInputStream("c.jpg"));
        BufferedOutputStream out = new BufferedOutputStream(socket.getOutputStream());
        byte b[] = new byte[1024];
        int len = 0;
        while ((len = in.read(b)) != -1) {
            out.write(b, 0, len);
            out.flush();    // 刷新缓冲区 要不然最后一块缓冲区字符串会缺失
        }
        socket.shutdownOutput();   // 关闭流以后Server段才会接收道结束字符结束接受
        BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        String line;
        while ((line = br.readLine()) != null) {
            System.out.println(line);
        }
        in.close();
        socket.close();
    }
}

UDP实现

UDP是将数据打成数据包向对方发送，只关系是否发送成功，而不关心是否接收成功，传输速度快，但是可靠性低。

udp代码实现

// 发送端
public class SendDemo {
    public static void main(String[] args) throws IOException {
        DatagramSocket ds = new DatagramSocket(); // 此类表示用来发送和接收数据报包的套接字。
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in)); // 键盘输入
        String line = null;
        while ((line = br.readLine()) != null) {
            byte[] bytes = line.getBytes();
            DatagramPacket dp = new DatagramPacket(bytes, bytes.length, InetAddress.getByName("127.0.0.1"), 10005); // 数据包对象
            ds.send(dp);
            if ("886".equals(line)) { // 当输入886时结束发送
                break;
            }
        }
        ds.close();
    }
}
// 接收端
public class ReciveDemo {
    public static void main(String[] args) throws IOException {
        DatagramSocket ds = new DatagramSocket(10005); // 建立服务端
        byte bytes[] = new byte[1024];
        DatagramPacket dp = new DatagramPacket(bytes, bytes.length); // 建立数据包对象
        while (true) {
            ds.receive(dp); // 接受数据包
            byte[] data = dp.getData(); // 获取数据
            String str = new String(data, 0, dp.getLength());
            if ("886".equals(str)) {
                break;
            }
            System.out.println(str);
        }
        ds.close();
    }
}