JAVA学习-网络编程
TCP实现聊天（Local）
服务端
package com.myTCP.chatDemo;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.net.ServerSocket;
import java.net.Socket;
public class ServerChat {
public static void main(String[] args) {
ServerSocket serverSocket = null;
Socket socket = null;
InputStream inputStream = null;
ByteArrayOutputStream baos = null;
try {
//服务端需要一个地址
serverSocket = new ServerSocket(829);
//服务端等待客户端的连接 accept方法，就是等待客户端连接
socket = serverSocket.accept();
//读取客户端消息
inputStream = socket.getInputStream();
//管道流用于输出
baos =new ByteArrayOutputStream();
byte[] bytes = new byte[1024];
int Len;
while ((Len = inputStream.read(bytes)) != -1){
baos.write(bytes,0 ,Len);
}
System.out.println(baos.toString());
} catch (IOException e) {
e.printStackTrace();
} finally {
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
package com.myTCP.chatDemo;
import java.io.IOException;
import java.io.OutputStream;
import java.net.InetAddress;
import java.net.Socket;
import java.net.UnknownHostException;
public class ClientChat {
public static void main(String[] args) {
Socket socket = null;
OutputStream os = null;
try {
//获得服务端IP
InetAddress serverIP = InetAddress.getByName("127.0.0.1");
//填写服务端IP和端口到客户端
socket = new Socket(serverIP,829);
//输出流连到客户端的输出方法
os = socket.getOutputStream();
//输出流输出内容
os.write("hello,world!".getBytes());
} catch (Exception e) {
e.printStackTrace();
} finally {
if (os != null){
try {
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (socket != null){
try {
socket.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
}
TCP文件上传（Local）
UDP发短信（Local）
初级
发送端
package com.myUDP.chatDemo01;
import java.net.*;
public class mySend {
public static void main(String[] args) {
DatagramSocket socket = null;
try {
socket = new DatagramSocket();
String msg ="hello,world";
InetAddress localhost = InetAddress.getByName("localhost");
int port = 829;
DatagramPacket packet = new DatagramPacket(msg.getBytes(),0,msg.length(),localhost,port);
socket.send(packet);
} catch (Exception e) {
e.printStackTrace();
} finally {
}
}
}
接收端
package com.myUDP.chatDemo01;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.Socket;
import java.net.SocketException;
public class myReceive {
public static void main(String[] args) {
DatagramSocket socket = null;
DatagramPacket packet = null;
try {
socket = new DatagramSocket(829);//设置自己接收的端口
byte[] buffer = new byte[1024];//缓冲区
packet = new DatagramPacket(buffer,0,buffer.length);//接收数据包
socket.receive(packet);//阻塞式监听
System.out.println(new String(packet.getData(),0,packet.getLength()));//输出数据包接收到的内容
} catch (Exception e) {
e.printStackTrace();
} finally {
if (socket != null){
socket.close();
}
}
}
}
实现控制台循环发送
发送端：
package com.myUDP.demo02;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.*;
public class Demo02 {
public static void main(String[] args) {
try {
DatagramSocket socket = new DatagramSocket(666) ;
while (true){
byte[] bytes = new byte[1024];
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
String sendBytes = reader.readLine();
bytes = sendBytes.getBytes();
InetAddress inetAddress = InetAddress.getLocalHost();
DatagramPacket packet = new DatagramPacket(bytes,0,bytes.length,inetAddress,888 );
socket.send(packet);
if (sendBytes.equals("bye")){
break;
}
}
socket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
接收端
package com.myUDP.demo02;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
public class Demo02b {
public static void main(String[] args) {
try {
DatagramSocket socket = new DatagramSocket(888);
while (true){
byte[] buff = new byte[1024];
DatagramPacket packet = new DatagramPacket(buff,0,buff.length);
socket.receive(packet);
System.out.println(new String(buff,0, packet.getLength()));//注意，这里必须是获取packet的长度，byte[]的长度是1024！！
if (new String(buff,0, packet.getLength()).equals("bye")){
break;
}
}
socket.close();
} catch (Exception e) {
e.printStackTrace();
}
}
}
实现多线程交互式聊天
发送消息线程
package com.myUDP.demo04;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
public class SendMsg implements Runnable{
DatagramSocket socket;
BufferedReader reader;
private int toIP;
private int fromIP;
public SendMsg(int toIP, int fromIP) {
this.toIP = toIP;
this.fromIP = fromIP;
}
@Override
public void run() {
try {
socket = new DatagramSocket(fromIP) ;
reader = new BufferedReader(new InputStreamReader(System.in));
while (true){
byte[] bytes = new byte[1024];
String sendBytes = reader.readLine();
bytes = sendBytes.getBytes();
InetAddress inetAddress = InetAddress.getLocalHost();
DatagramPacket packet = new DatagramPacket(bytes,0,bytes.length,inetAddress,toIP );
socket.send(packet);
if (sendBytes.equals("bye")){
break;
}
}
socket.close();
System.exit(0);
} catch (Exception e) {
e.printStackTrace();
}
}
}
接收消息线程
package com.myUDP.demo04;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
public class ReceiveMsg implements Runnable{
DatagramSocket socket;
private int recIP;
private String recName;
public ReceiveMsg(int recIP, String recName) {
this.recIP = recIP;
this.recName = recName;
}
@Override
public void run() {
try {
socket = new DatagramSocket(recIP);
while (true){
byte[] buff = new byte[1024];
DatagramPacket packet = new DatagramPacket(buff,0,buff.length);
socket.receive(packet);
System.out.println(recName+":"+new String(buff,0, packet.getLength()));//注意，这里必须是获取packet的长度，byte[]的长度是1024！！
if (new String(buff,0, packet.getLength()).equals("bye")){
break;
}
}
socket.close();
System.exit(0);
} catch (Exception e) {
e.printStackTrace();
}
}
}
客户端启动线程
package com.myUDP.demo04;
public class Student {
public static void main(String[] args) {
new Thread(new SendMsg(888,01)).start();
new Thread(new ReceiveMsg(666,"老师")).start();
}
}
////////////////////////////////
package com.myUDP.demo04;
public class Teacher {
public static void main(String[] args) {
new Thread(new SendMsg(666,02)).start();
new Thread(new ReceiveMsg(888,"学生")).start();
}
}
关于try-catch遇到的问题
注意一个问题！！！ try-catch 里面new的对象一旦离开了try-catch就没了，会出现空指针异常。
但如果是放在构造器里面，相当于一出生就new了，是可以使用的！！！
例如，举个例子，发送线程：
package com.myUDP.demo03;
import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.DatagramPacket;
import java.net.DatagramSocket;
import java.net.InetAddress;
import java.net.SocketException;
public class SendMsg implements Runnable {
DatagramSocket socket = null;
DatagramPacket packet = null;
private int toPort;
private int formPort;
BufferedReader reader = null;
public SendMsg( int toPort, int formPort) {
this.toPort = toPort;
this.formPort = formPort;
try {
this.socket = new DatagramSocket(formPort);
this.reader = new BufferedReader(new InputStreamReader(System.in));
} catch (SocketException e) {
e.printStackTrace();
}
}
@Override
public void run() {
try {
while (true){
//String sendBytes = this.reader.readLine();
byte[] bytes = this.reader.readLine().getBytes(); //这里不要定义1024，因为不清楚具体长度
this.packet = new DatagramPacket(bytes,0,bytes.length,InetAddress.getLocalHost(),toPort);
this.socket.send(packet);
String sendBytes = new String(bytes,0, bytes.length);
if (sendBytes.equals("bye")){
break;
}
socket.close();
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
URL下载网络资源
package com.myURL.demo01;
import javax.net.ssl.HttpsURLConnection;
import java.io.FileOutputStream;
import java.io.InputStream;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;
public class Demo01 {
public static void main(String[] args) {
try {
URL url = new URL("https://i1.hdslb.com/bfs/face/15f6459eb358579aeb524f8620d624ab181b6373.jpg@96w_96h_1c_1s.webp");
//连接到这个资源
HttpsURLConnection connection = (HttpsURLConnection) url.openConnection();
//利用IO流下载
InputStream inputStream = connection.getInputStream();
FileOutputStream fileOutputStream = new FileOutputStream("1.web");
byte[] buffer = new byte[1024];
int len;
if ((len = inputStream.read(buffer)) != -1){
fileOutputStream.write(buffer,0,len);
}
} catch (Exception e) {
e.printStackTrace();
}
}
}
