Java学习网络编程

大纲

网络相关概念
IP地址
网络协议
InetAdress
Socket

具体案例

1. 网络相关概念

网络
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网络通信

2. IP地址

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域名

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3.网络协议

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4. InetAdress

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获得本机的名字和IP

 public static void main(String[] args) throws UnknownHostException {InetAddress inetAddress = InetAddress.getLocalHost();System.out.println(inetAddress);}

获取指定主机名字或域名的信息

public static void main(String[] args) throws UnknownHostException {InetAddress host1 = InetAddress.getByName("  ");InetAddress host2 = InetAddress.getByName("www.baidu.com");System.out.println(host1);System.out.println(host2);}

gethostname 是获取主机名字。或者域名
getHostAddress 是获取IP地址

public static void main(String[] args) throws UnknownHostException {InetAddress host1 = InetAddress.getByName("挽天");InetAddress host2 = InetAddress.getByName("www.baidu.com");String f2 = host2.getHostAddress();String f1 = host1.getHostAddress();String name = host2.getHostName();System.out.println(f1);System.out.println(f2);System.out.println(name);}

5. Socket

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TCP编程

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当客户端连接服务端时，服务端是我们固定的端口，而客户端也有一个端口，只不过是TCP/IP协议随机分配的

结束标记
通用：调用socket对象的shutdownOutput()方法
其它：在写入时可以用writeNewLine（）来进行结束标记，但这要求读取必须使用readline（）方法
注意：写完过后记得使用flush方法刷新
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服务端

public class socketServer {public static void main(String[] args) throws IOException {//服务端//在本机的9999端口监听，等待连接//前提该端口没有被占用//这个serverSocket,可以通过accept()来返回多个socket(高并发,多个客户端来连接服务器端)ServerSocket serverSocket = new ServerSocket(9999);//当没有客户端连接该端口时。程序会堵塞等待连接//  如果在客户端连接，就会返回Socket对象,程序继续执行Socket socket = serverSocket.accept();//创建一个和这个socket相关的输入流InputStream inputStream = socket.getInputStream();byte [] buf = new byte[1024];int length = 0;while ((length = inputStream.read(buf)) != -1){//根据读取到的实际长度读取字符串System.out.println(new String(buf,0,length));}//创建一个socket相关的输出流OutputStream outputStream = socket.getOutputStream();outputStream.write("hello,client".getBytes());outputStream.flush();//设置一个结束标记代表传入结束socket.shutdownOutput();//关闭流inputStream.close();outputStream.close();//关闭这个对象socket.close();serverSocket.close();}
}

客户端

public class socketClient {public static void main(String[] args) throws IOException {//客户端//连接服务器，里面写一个主机地址和端口，这里写的是本机//如果联机成功，返回一个socket对象Socket socket = new Socket(InetAddress.getLocalHost(),9999);//得到一个和socket对象关联的输出流OutputStream outputStream = socket.getOutputStream();//通过输出流，写入数据到数据通道outputStream.write("hello,server".getBytes());outputStream.flush();//设置一个结束标记socket.shutdownOutput();//获取和与socket相关联的输入流InputStream inputStream = socket.getInputStream();byte[] bytes = new byte[1024];int length;//创建循环读取数据while ((length = inputStream.read(bytes)) != -1){System.out.println(new String(bytes,0,length));}//关闭流对象，和socket，避免资源浪费inputStream.close();outputStream.close();socket.close();}
}

第二题：
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服务端：

public class server1 {public static void main(String[] args) throws IOException {//创建等待接收ServerSocket serverSocket = new ServerSocket(8888);Socket socket = serverSocket.accept();//创建一个与socket相关的输入流BufferedInputStream bis = new BufferedInputStream(socket.getInputStream());//把接收的数据存入一个byte数组byte[] bytes = tool.readArray(bis);String fileName = "D:\\java学习\\掉毛.jpg";//创建一个输出流BufferedOutputStream bos = new BufferedOutputStream(new FileOutputStream(fileName));//把得到的数据写入磁盘bos.write(bytes);bos.close();//创建一个与socket相关的输出流BufferedWriter writer = new BufferedWriter(new OutputStreamWriter(socket.getOutputStream()));//传递信息writer.write("收到图片");writer.flush();socket.shutdownOutput();//关闭流bis.close();writer.close();socket.close();serverSocket.close();}
}

客户端:

public class client1 {public static void main(String[] args) throws IOException {Socket socket = new Socket(InetAddress.getLocalHost(), 8888);String fileName = "D:\\java学习\\图片\\蛋糕.jpg";//创建一个输入流。从磁盘读取信息BufferedInputStream bis = new BufferedInputStream(new FileInputStream(fileName));//把读取到的信息存入一个字节数组byte [] bytes = tool.readArray(bis);//创建一个与socket相关的输出流BufferedOutputStream bos = new BufferedOutputStream(socket.getOutputStream());//传出数据bos.write(bytes);socket.shutdownOutput();//创建一个与socket相关的输入流InputStream inputStream = socket.getInputStream();//读取信息，并返回一个字符串String s = tool.readString(inputStream);//输出信息System.out.println(s);//关闭资源inputStream.close();socket.close();bos.close();bis.close();}
}

工具类：

public class  tool {public static byte [] readArray(InputStream is) throws IOException {ByteArrayOutputStream bos = new ByteArrayOutputStream();byte[] bytes = new byte[1024];int len;while ((len = is.read(bytes)) != -1){bos.write(bytes,0,len);}byte [] array = bos.toByteArray();bos.close();return array;}public static String readString (InputStream is) throws IOException {BufferedReader reader = new BufferedReader(new InputStreamReader(is));StringBuilder stringBuilder = new StringBuilder();String line;while ((line = reader.readLine()) != null){stringBuilder.append(line + "\r\n");}return stringBuilder.toString();}
}

netstat指令

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UDP编程

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接收端/发送端：

public class UDPReceive {public static void main(String[] args) throws IOException {//创建一个 DatagramSocket对象DatagramSocket datagramSocket = new DatagramSocket(9999);//构建一个DatagramPacket,传入bytes数组byte[] bytes = new byte[64 * 1024];DatagramPacket packet = new DatagramPacket(bytes, bytes.length);//调用接收方法接收数据//把接收到的数据，填充到DatagramPacket里面去//这个receive方法，没有接收到数据，程序就会阻塞datagramSocket.receive(packet);//进行拆包,并显示内容int length = packet.getLength();//得到长度byte [] data = packet.getData();//得到数组String s = new String (data,0,length);System.out.println(s);//发送内容byte[] bytes1 = "好的，明天见".getBytes();packet = new DatagramPacket(bytes1, bytes1.length, InetAddress.getByName("192.168.101.8"), 8888);datagramSocket.send(packet);//关闭流datagramSocket.close();}
}

发送端/接收端：

public class UDPSend {public static void main(String[] args) throws IOException {//创建一个DatagramSocket准备在8888端口发送,接收数据DatagramSocket datagramSocket = new DatagramSocket(8888);//将需要发送的数据封装到DatagramPacket//传入byte数组，数组长度，目标地址和端口byte[] bytes = "hello,明天吃火锅".getBytes();DatagramPacket packet = new DatagramPacket(bytes, bytes.length, InetAddress.getByName("192.168.101.8"), 9999);//发出数据datagramSocket.send(packet);//接收数据byte[] bytes1 = new byte[1024 * 64];packet = new DatagramPacket(bytes1, bytes1.length);datagramSocket.receive(packet);byte[] data = packet.getData();int length = packet.getLength();String s = new String(data,0,length);System.out.println(s);//关闭流datagramSocket.close();}
}