java之网络
Posted scanner小霸王
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网络通信
网络：
ip地址（唯一标识主机）：
ipv4：4个字节(32位)表示；一个字节的范围是0~255，
（0255）.（0255）.（0255）.（0255）
ip地址的组成：网络地址+主机地址；比如：192.168.16.69;其中192.168.16是网络地址，69是主机地址；
ipv6使用128位表示地址，16个字节，是ipv6的四倍（.......）
ipv4的分类：
在开发中0~1024端口尽量不用
域名和端口（监听一个服务才需要端口）：
在
网络通信协议：
网络通信理解：
tcp/ip协议：
用户发送数据时候要打包，用户结束接收数据的时候要拆包
TCP和UDP
InetAddress类
Socket类
（可以当做数据通道两端的插头）
Socket的理解：
Socket通讯完成是需要关闭的，英文Socket的连接的数量是有限的
逻辑分析：
代码实现：
字节传输实例一：
ServerSocket可以创建多个Socket
客户端
public class TcpClient
public static void main(String[] args) throws UnknownHostException, IOException
//1.连接服务器（ip,端口）
Socket socket = new Socket(InetAddress.getLocalHost(),9999);
//2连接上后，生成SOcket，通过socket.getOutputStream得到输出流
OutputStream outputStream = socket.getOutputStream();
//3往输出流写入数据
outputStream.write("hello".getBytes());
//4.设置写入结束（否则将陷入阻塞）
socket.shutdownOutput();
//5.接受服务端的输入流
InputStream inputStream = socket.getInputStream();
byte[] buff = new byte[1024];
int len;
while ((len=inputStream.read(buff))!=-1)
System.out.println("tcpClient读取："+new String(buff,0,len));
//6.关闭
inputStream.close();
outputStream.close();
socket.close();
System.out.println("客户端退出--");
服务端：
package file;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class TcpServer
public static void main(String[] args) throws IOException
//1监听9999端口
ServerSocket serverSocket = new ServerSocket(9999);
//2等待连接，连接
//如果有客户端连接，将返回Socket对象
Socket socket = serverSocket.accept();
System.out.print("socket:"+socket.getClass());
//3.通过socket.getInputStream()读取客户端的数据
InputStream inputStream = socket.getInputStream();
byte[] bytes = new byte[1024];
int len =0;
//4.Io读取
while((len = inputStream.read(bytes))!=-1)
System.out.print("serverSocket读取 "+new String(bytes,0,len));
//5.写出一句话
OutputStream outputStream = socket.getOutputStream();
outputStream.write("serverSocket写出".getBytes());
//6.设置写入结束
socket.shutdownOutput();
//5.关闭流和Io
outputStream.close();
inputStream.close();
socket.close();
serverSocket.close();
字符传输：
也可以writer.newLine()作为接受标记，但是读数据就需要采用readLine（）
客户端：
public class TcpClient
public static void main(String[] args) throws UnknownHostException, IOException
//1.连接服务器（ip,端口）
Socket socket = new Socket(InetAddress.getLocalHost(),9999);
//2连接上后，生成SOcket，通过socket.getOutputStream得到输出流
OutputStream outputStream = socket.getOutputStream();
//3往输出流写入数据
outputStream.write("hello".getBytes());
//4.设置写入结束（否则将陷入阻塞）
socket.shutdownOutput();
//5.接受服务端的输入流
InputStream inputStream = socket.getInputStream();
/*byte[] buff = new byte[1024];
int len;
while ((len=inputStream.read(buff))!=-1)
System.out.println("tcpClient读取："+new String(buff,0,len));
*/
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));
char [] chars =new char[100];
int len;
while ((len=bufferedReader.read(chars))!=-1)
System.out.println("tcpClient读取："+new String(chars,0,len));
bufferedReader.close();
//6.关闭
inputStream.close();
outputStream.close();
socket.close();
System.out.println("客户端退出--");
服务端：
public class TcpServer
public static void main(String[] args) throws IOException
//1监听9999端口
ServerSocket serverSocket = new ServerSocket(9999);
//2等待连接，连接
//如果有客户端连接，将返回Socket对象
Socket socket = serverSocket.accept();
System.out.print("socket:"+socket.getClass());
//3.通过socket.getInputStream()读取客户端的数据
InputStream inputStream = socket.getInputStream();
byte[] bytes = new byte[1024];
int len =0;
//4.Io读取
while((len = inputStream.read(bytes))!=-1)
System.out.print("serverSocket读取 "+new String(bytes,0,len));
//5.写出一句话
OutputStream outputStream = socket.getOutputStream();
// outputStream.write("serverSocket写出".getBytes());
BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream));
bufferedWriter.write("serverSocket写出");
//字节流需要手动刷新
bufferedWriter.flush();
//6.设置写入结束
socket.shutdownOutput();
//5.关闭流和Io
outputStream.close();
inputStream.close();
socket.close();
serverSocket.close();
服务端：
package 网络;
import java.io.BufferedInputStream;
public class TcpServer2
public static void main(String[] args) throws IOException
//1监听9999端口
ServerSocket serverSocket = new ServerSocket(9999);
//2等待连接，连接
//如果有客户端连接，将返回Socket对象
Socket socket = serverSocket.accept();
//3.通过socket.getInputStream()读取客户端的数据
BufferedInputStream bufferedInputStream = new BufferedInputStream(socket.getInputStream());
//4.将客户端的二进制内容转为数组，
byte[] buff = StreamUtils.streamToByteArray(bufferedInputStream);
//5.创建保存文件路径的输出流
BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream("src/12.jpg"));
bufferedOutputStream.write(buff);
//6.回复消息给客户端
BufferedWriter bufferedWriter =new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));
bufferedWriter.write("收到图片");
bufferedWriter.flush();//把内容刷入数据通道
socket.shutdownOutput();//设置写入结束标记
//7.关闭流和Io
bufferedWriter.close();
bufferedOutputStream.close();
bufferedInputStream.close();
socket.close();
serverSocket.close();
客户端：
package 网络;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.BufferedReader;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
public class TcpClient2
public static void main(String[] args) throws UnknownHostException, IOException
//1.连接服务器（ip,端口）
Socket socket = new Socket(InetAddress.getLocalHost(),9999);
//2.包装流，读取数据
BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream("E:/照片/12.jpg"));
//3.将数据转为字节数组
byte[] bytes =StreamUtils.streamToByteArray(bufferedInputStream);
//4往输出流写入数据
BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(socket.getOutputStream());
bufferedOutputStream.write(bytes);
//5.设置写入数据的结束标记(注意：socket.shutdownOutput();
//写完之后就应该执行该语句，一开始我误认为可以在文中最后关闭，结果程序阻塞了)
socket.shutdownOutput();
//6.接受服务器反馈回来的消息,
InputStream inputStream = socket.getInputStream();
//7.将流的内容转为字符串
String s = StreamUtils.streamToString(inputStream);
System.out.println("客户端接受到消息："+s);
//8.关闭
System.out.println("客户端退出--");
socket.close();
bufferedInputStream.close();
bufferedOutputStream.close();
inputStream.close();
工具类：
package 网络;
import java.io.BufferedReader;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
public class StreamUtils
/**
* 输出流转化为byte[]
* @param is
* @return
* @throws IOException
*/
public static byte[] streamToByteArray(InputStream is) throws IOException
ByteArrayOutputStream bos = new ByteArrayOutputStream();
byte[] b = new byte[1024];
int len;
while((len = is.read(b))!=-1)
bos.write(b,0,len);
byte[] array = bos.toByteArray();
bos.close();
return array;
public static String streamToString(InputStream is) throws IOException
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(is));
StringBuilder stringBuilder = new StringBuilder();
String line;
while((line = bufferedReader.readLine())!=null)
stringBuilder.append(line+"\\r\\n");
return stringBuilder.toString();
netstat指令：
UDP
基本流程：
例子：
发送端A和发送端B各自发送一句，各自回复一句；
（既是发送端口，也是接收端口）
发送端A：
package MyCode.UDP;
import java.io.IOException;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
public class UDPSendA
public static void main(String[] args) throws IOException
//1创建DatagramSocket对象，准备再9998端口接收数据
DatagramSocket datagramSocket = new DatagramSocket(9999);
//2准备接收数据
byte[] buff = new byte[1024];
//InetAddress.getLocalHost()这里是本机自己玩，也可以InetAddress.getByName(ip)
DatagramPacket datagramPacket = new DatagramPacket(buff, buff.length);
//3.接收，当有数据包发送到9999就会接收到数据，否则，将会阻塞等待
datagramSocket.receive(datagramPacket);
//4.拆包
int length = datagramPacket.getLength();
byte[] data = datagramPacket.getData();
String s = new String(data,0,length);
System.out.println("A端收到消息："+s);
//5.回复消息给B
//将需要发送的数据，封装到DatagramPacket对象
byte[] data2 = "我是A端，我收到消息了".getBytes();
//InetAddress.getLocalHost()这里是本机自己玩，也可以InetAddress.getByName(ip)
datagramPacket = new DatagramPacket(data2, data2.length, InetAddress.getLocalHost(), 9998);
datagramSocket.send(datagramPacket);
//关闭
datagramSocket.close();
System.out.println("A端退出");
接收端：
package MyCode.UDP;
import java.io.IOException;
import java.net.*;
public class UDPSendB
public static void main(String[] args) throws IOException
//1创建DatagramSocket对象，准备再9998端口接收数据
DatagramSocket datagramSocket = new DatagramSocket(9998);
//2将需要发送的数据，封装到DatagramPacket对象
byte[] data = "hello 你好，我是B端".getBytes();
//InetAddress.getLocalHost()这里是本机自己玩，也可以InetAddress.getByName(ip)
DatagramPacket datagramPacket = new DatagramPacket(data, data.length, InetAddress.getLocalHost(), 9999);
datagramSocket.send(datagramPacket);
//3准备接收数据
byte[] buff = new byte[1024];
//InetAddress.getLocalHost()这里是本机自己玩，也可以InetAddress.getByName(ip)
datagramPacket = new DatagramPacket(buff, buff.length);
//4.接收，当有数据包发送到9999就会接收到数据，否则，将会阻塞等待
datagramSocket.receive(datagramPacket);
//5.拆包
int length = datagramPacket.getLength();
data = datagramPacket.getData();
String s = new String(data,0,length);
System.out.println("B端收到消息:"+s);
//关闭
datagramSocket.close();
System.out.println("B端退出");
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