打算将 Socket 编程再复习下，为后续学习 netty 做准备。
知识准备
学习 Socket 编程，一些前置知识必不可少。
OSI 参考模型以及 TCP/IP 协议栈。
网络编程三要素：协议、IP 和端口号。
端口号是正在运行的程序的标识；有效的端口号范围：0 到 65535，其中 0 到 1024 为系统使用或保留。
TCP/IP 是对一组协议的统称，具体每一层都有很多协议。传输层的协议主要关注 TCP 和 UDP。
UDP 的特点是无连接、速度快、不可靠，需要将数据打包，有大小限制。
TCP 的特点是有连接（三次握手、四次挥手），速度相比 UDP 要慢，但要可靠，数据无限制。
Socket 编程，即为网络编程，也称为套接字编程。Socket 是网络上具有唯一标识的 IP 地址和端口号组合在一起构成。Socket 通信的两端都有 Socket，网络通信即为 Socket 间的通信，数据在两个 Socket 间在某种协议下通过 IO 流传输。
API 学习
关于 Java Socket 的源码都在 net 包下，其中有几个比较重要的类 InetAddress 和 URL 等等。
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| package com.nekolr;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.InetAddress;
import java.net.URL;
public class APIDemo {
public static void main(String[] args) throws Exception {
InetAddress address = InetAddress.getLocalHost();
String hostName = address.getHostName();
String ip = address.getHostAddress();
byte []bytes = address.getAddress();
InetAddress address1 = InetAddress.getByName("avalon");
InetAddress address2 = InetAddress.getByName("192.168.229.1");
InetAddress address3 = InetAddress.getByAddress(bytes);
URL baidu = new URL("http://www.baidu.com");
URL url = new URL(baidu, "/index.html?username=nekolr#test");
url.getProtocol();
url.getHost();
url.getPort();
url.getPath();
url.getFile();
url.getRef();
url.getQuery();
InputStream is = baidu.openStream();
InputStreamReader isr = new InputStreamReader(is, "utf-8");
BufferedReader br = new BufferedReader(isr);
String line = br.readLine();
while (line!=null){
System.out.println(line);
line = br.readLine();
}
br.close();
isr.close();
is.close();
try (BufferedReader reader = new BufferedReader(new InputStreamReader(baidu.openStream(), "utf-8"))) {
String data;
while((data = reader.readLine())!=null){
System.out.println(data);
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
|
简单 Socket 通信练习
Socket 通信基于 TCP 和 UDP 协议，针对这两个协议有不同的写法。
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| import java.io.*;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.concurrent.*;
public class TcpSocket {
static class TcpServer implements Runnable {
private int port;
public TcpServer(int port) {
this.port = port;
}
@Override
public void run() {
ServerSocket serverSocket = null;
BufferedReader reader = null;
BufferedWriter writer = null;
try {
serverSocket = new ServerSocket(this.port);
Socket socket = serverSocket.accept();
reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
System.out.println("Client Message：" + reader.readLine());
writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
writer.write("Hello Client");
writer.newLine();
writer.flush();
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (serverSocket != null) serverSocket.close();
if (reader != null) reader.close();
if (writer != null) writer.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
static class TcpClient implements Runnable {
private String host;
private int port;
public TcpClient(String host, int port) {
this.host = host;
this.port = port;
}
@Override
public void run() {
Socket socket = null;
BufferedWriter writer = null;
BufferedReader reader = null;
try {
socket = new Socket(this.host, this.port);
writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
writer.write("Hello Server");
writer.newLine();
writer.flush();
reader = new BufferedReader(new InputStreamReader(socket.getInputStream()));
System.out.println("Server Message：" + reader.readLine());
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
if (socket != null) socket.close();
if (reader != null) reader.close();
if (writer != null) writer.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
}
public static void main(String[] args) {
TcpServer tcpServer = new TcpServer(8888);
TcpClient tcpClient = new TcpClient("localhost", 8888);
ExecutorService executor = new ThreadPoolExecutor(2, 2,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<>(1024), new ThreadPoolExecutor.AbortPolicy());
executor.execute(tcpServer);
executor.execute(tcpClient);
}
}
|
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| import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
import java.util.concurrent.*;
public class UdpSocket {
static class UdpServer implements Runnable {
private int clientPort = 10088;
private int serverPort = 10086;
private String host = "localhost";
@Override
public void run() {
try (DatagramSocket socket = new DatagramSocket(serverPort)) {
byte[] bytes = "我是服务端，消息为：i'm server".getBytes();
DatagramPacket sendPacket = new DatagramPacket(bytes, bytes.length, InetAddress.getByName(host), clientPort);
socket.send(sendPacket);
bytes = new byte[1024];
DatagramPacket receivePacket = new DatagramPacket(bytes, bytes.length);
socket.receive(receivePacket);
System.out.println("服务端接收的消息为：" + new String(bytes, "utf-8"));
} catch (SocketException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
static class UdpClient implements Runnable {
private int clientPort = 10088;
private int serverPort = 10086;
private String host = "localhost";
@Override
public void run() {
try (DatagramSocket socket = new DatagramSocket(clientPort)) {
byte[] bytes = "我是客户端，消息为：i'm client".getBytes();
DatagramPacket sendPacket = new DatagramPacket(bytes, bytes.length, InetAddress.getByName(host), serverPort);
socket.send(sendPacket);
bytes = new byte[1024];
DatagramPacket receivePacket = new DatagramPacket(bytes, bytes.length);
socket.receive(receivePacket);
System.out.println("客户端接收的消息为：" + new String(bytes, "utf-8"));
} catch (SocketException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
}
public static void main(String[] args) {
UdpServer udpServer = new UdpServer();
UdpClient udpClient = new UdpClient();
ExecutorService executor = new ThreadPoolExecutor(2, 2,
0L, TimeUnit.MILLISECONDS,
new LinkedBlockingQueue<>(1024), new ThreadPoolExecutor.AbortPolicy());
executor.execute(udpServer);
executor.execute(udpClient);
}
}
|