入门
c/s：Client/Server结构，客户端和服务器
B/S：Browser/Server结构，浏览器和服务器
java.net包中提供了两种常见的网络协议的支持：
- UDP：用户数据报协议。无连接，数据限制在64kb以内
- TCP：传输控制协议。有连接，三次握手
网络编程三要素
- 协议
- IP
- 端口
计算机网络
网络编程的目的：传播、交流信息
IP、端口、通信协议
IP
InetAddress
public class App {
public static void main(String[] args) {
try {
InetAddress address = InetAddress.getByName("127.0.0.1");
System.out.println(address);
InetAddress address2 = InetAddress.getByName("localhost");
System.out.println(address2);
InetAddress address3 = InetAddress.getLocalHost();
System.out.println(address3);
InetAddress address4 = InetAddress.getByName("www.baidu.com");
System.out.println(address4);
//常用方法
System.out.println(address4.getAddress());
System.out.println(address4.getCanonicalHostName());//规范的名字
System.out.println(address4.getHostAddress());//ip
System.out.println(address4.getHostName());//域名，或者自己电脑的名字
} catch (UnknownHostException e) {
e.printStackTrace();
}
}
}
端口
一个端口对应一个程序的进程
- 范围0-65535
- TCP和UDP各有0-65535
- 端口分类
- 共有端口0-1023
- HTTP:80
- HTTS:443
- FTP:21
- Telent：23
- 程序注册端口：1024-49151，分配用户或者程序
- Tomcat:8080
- mysql:3306
- Oracle:1521
- 动态、私有：49152-65535
- 共有端口0-1023
netstat -ano #查看所有的端口
netstat -ano|findstr "5900" #查看指定的端口
tasklist|findstr "8696" #查看指定端口的进程
public class PortDemo {
public static void main(String[] args) {
InetSocketAddress socketAddress = new InetSocketAddress("127.0.0.1", 8080);
InetSocketAddress socketAddress2 = new InetSocketAddress("localhost", 8080);
System.out.println(socketAddress);
System.out.println(socketAddress2);
System.out.println(socketAddress.getAddress());
System.out.println(socketAddress.getHostName());
System.out.println(socketAddress.getPort());
}
}
通信协议
网络通信：速率、传输码率、代码结构、传输控制……
重要：
- TCP：用户传输协议——打电话
- 连接、稳定
- 三次握手、四次挥手
- 客户端、服务端
- 传输完成、释放连接、效率低
- UDP：用户数据协议——发短信
- 不连接、不稳定
- 客户端、服务器没有明确的界限
- 不管有没有准备好，都可以发给你
- DDOS：洪水攻击
TCP实现聊天
服务器
- 建立服务的端口 ServerSocket
- 等待用户的连接 Socket.accept()
- 接收客户端消息
客户端
- 连接服务器Socket
- 发送消息
//服务端
public class ServerDemo1 {
public static void main(String[] args) {
ServerSocket serverSocket = null;
Socket socket = null;
InputStream inputStream = null;
ByteArrayOutputStream baos = null;
try {
//1、一个地址
serverSocket = new ServerSocket(9999);
//2、等待客户端连接过来
socket = serverSocket.accept();
//3、读取客户端消息
inputStream = socket.getInputStream();
//管道流
baos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int len;
while((len=inputStream.read(buffer))!=-1){
baos.write(buffer,0,len);
}
System.out.println(baos.toString());
} catch (IOException e) {
e.printStackTrace();
}finally {
//关闭资源
if(baos!=null){
try {
baos.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(inputStream!=null){
try {
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(socket!=null){
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(serverSocket!=null){
try {
serverSocket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
//客户端
public class ClientDemo1 {
public static void main(String[] args) {
Socket socket = null;
OutputStream outputStream = null;
try {
//1、知道服务器的地址，端口号
InetAddress serverIP = InetAddress.getByName("127.0.0.1");
int port = 9999;
//2、创建一个socket连接
socket = new Socket(serverIP,port);
//3、发送消息，io流
outputStream = socket.getOutputStream();
outputStream.write("你好,欢迎来到未来世界".getBytes());
} catch (Exception e) {
e.printStackTrace();
}finally {
if(outputStream!=null){
try {
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if(socket!=null){
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
TCP文件上传
//客户端
public class ClientDemo2 {
public static void main(String[] args) throws IOException {
//1、创建一个Socket连接
Socket socket = new Socket(InetAddress.getByName("127.0.0.1"),9999);
//2、创建一个输出流
OutputStream os = socket.getOutputStream();
//3、读取文件
FileInputStream fileInputStream = new FileInputStream(new File("F:\1.png"));
//4、写出文件
byte[] buffer = new byte[1024];
int len;
while((len=fileInputStream.read(buffer))!=-1){
os.write(buffer,0,len);
}
//通知服务器，我已经结束了
socket.shutdownOutput();
//确定服务器接收完毕，才能断开连接
InputStream inputStream = socket.getInputStream();
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buffer2 = new byte[1024];
int len2;
while((len=inputStream.read(buffer2))!=-1){
baos.write(buffer2,0,len);
}
System.out.println(baos.toString());
//5、关闭资源
baos.close();
inputStream.close();
fileInputStream.close();
os.close();
socket.close();
}
}
//服务端
public class ServerDemo2 {
public static void main(String[] args) throws IOException {
//1、创建服务
ServerSocket serverSocket = new ServerSocket(9999);
//2、监听客户端的连接
Socket socket = serverSocket.accept();//阻塞式监听
//3、获取输入流
InputStream inputStream = socket.getInputStream();
//4、文件输出
FileOutputStream fileOutputStream = new FileOutputStream(new File("receive.png"));
byte[] buffer = new byte[1024];
int len;
while((len=inputStream.read(buffer))!=-1){
fileOutputStream.write(buffer,0,len);
}
//通知客户端我接收完毕了
OutputStream outputStream = socket.getOutputStream();
outputStream.write("我接收完毕了，你可以断开了".getBytes());
//5、关闭资源
fileOutputStream.close();
inputStream.close();
socket.close();
serverSocket.close();
}
}
Tomcat
UDP消息发送
public class UdpClient1 {
public static void main(String[] args) throws Exception {
//1、建立一个Socket
DatagramSocket socket = new DatagramSocket();
//2、建个包
String msg = "你好阿,服务器";
//发送给谁
InetAddress localhost = InetAddress.getByName("localhost");
int port = 9999;
DatagramPacket packet = new DatagramPacket(msg.getBytes(), 0, msg.getBytes().length, localhost, port);
//3、发送包
socket.send(packet);
//4、关闭流
socket.close();
}
public class UdpServer1 {
public static void main(String[] args) throws IOException {
//开放端口
DatagramSocket socket = new DatagramSocket(9999);
//接收数据包
byte[] buffer = new byte[1024];
DatagramPacket packet = new DatagramPacket(buffer, 0, buffer.length);
socket.receive(packet);
System.out.println(new String(packet.getData(),0,packet.getLength()));
//关闭连接
socket.close();
}
}