黑马程序员 Java网络传输UDP和TCP协议

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Java网络编程是由Socket类来实现，网络传输有UDP和TCP协议，前者不需要服务器端，通过数据包封装传输，数据传输最多64k，后者直接建立Socket流连接，可传输很大数据

需求:Java建立两个程序，用UDP协议实现发送端发送消息，接收端能接收到。

import java.net.*;
import java.io.*;
public class UdpSend{

public void getHost(String ipAddress)
{
try{

java.net.InetAddress ia = InetAddress.getByName(ipAddress);
String ip = ia.getHostAddress();
String name= ia.getHostName();
System.out.println(ip);
System.out.println(name);
}
catch(Exception e)
{
e.printStackTrace();
}
}

public void udpSendData() throws Exception
{

DatagramSocket ds = new DatagramSocket(8087);
//发送的内容编码为字节数组，数据原为键盘录入
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
String line = null;
while((line=br.readLine())!=null)
{
if("886".equals(line))
break;
byte [] by = line.getBytes();
//发送的地址
InetAddress ia = InetAddress.getByName("192.168.0.149");
//将发送数据封装成包的形式
DatagramPacket dp = new DatagramPacket(by,0,by.length,ia,1212);

ds.send(dp);

}
br.close();
ds.close();

}
public static void main(String [] args) throws Exception
{
UdpSend ur = new UdpSend();
ur.udpSendData();
}

}

class UdpReceive{

public void udpReceiveData() throws Exception
{

DatagramSocket ds = new DatagramSocket(1212);
while(true)
{
//接收的内容
byte[] by = new byte[1024];

//将发送数据封装成包的形式
DatagramPacket dp = new DatagramPacket(by,by.length);

ds.receive(dp);//堵塞式接收
//接收到的数据解码字符串
String data = new String(dp.getData(),0,dp.getLength());

System.out.println(dp.getAddress().getHostAddress()+"::"+data+
"::"+dp.getPort());

}
}

public static void main(String [] args) throws Exception
{
UdpReceive ur = new UdpReceive();
ur.udpReceiveData();
}

}

需求2：用UDP协议实现聊天程序

基本思路：使用一个main函数，建立两个线程，分别是发送消息和接收消息，同时运行两个线程

需求3：用TCP协议实现服务器端和客户端的通讯，需要保证当客户端连接上时，服务器端知道客户端的ip地址，并且服务器端能收到客户端发过来的信息。

如果有多个客户端连接服务器时，需要使用多线程，才能保证服务器端数据安全。

import java.util.*;
import java.net.*;
import java.io.*;
public class ThreadDemo {

/**
*源：Socket读取流
*目的：Socket输出流
**/
public void serverTcp() throws Exception{

ServerSocket ss = new ServerSocket(8001);
while(true)
{
Socket s = ss.accept();//阻塞式等待连接
//获取连接客户端的ip地址
new Thread(new ServerThread(s)).start();

}
}

public static void main(String[] args) throws Exception
{
ThreadDemo td = new ThreadDemo();
td.serverTcp();
}

}
class ClientTcp{

public void ClientTcp() throws Exception{

Socket s = new Socket();
InetAddress ia = InetAddress.getByName("192.168.0.149");
s.connect(new InetSocketAddress(ia,8001));
while(true)
{
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
OutputStream os = s.getOutputStream();
PrintWriter pw = new PrintWriter(os,true);//自动刷新
String line = br.readLine();
pw.println(line);
if("over".equals(line))
break;
}
}
public static void main(String[] args) throws Exception
{
ClientTcp td = new ClientTcp();
td.ClientTcp();
}
}
class ServerThread implements Runnable{

Socket s;
ServerThread(Socket s){
this.s=s;
}
public void run ()
{
try{
String ip = s.getInetAddress().getHostAddress();

System.out.println(ip+" 客户端连接上......");

while(true){

InputStream is = s.getInputStream();

BufferedReader br = new BufferedReader(new InputStreamReader(is));

String line = br.readLine();
if("over".equals(line))
break;
System.out.println(line);

}
System.out.println(ip+" 客户端断开......");
}
catch(Exception e)
{
new RuntimeException("接受失败");
}

}
}

由于Tcp协议客户端和服务器端都是使用阻塞式方法，当出现程序没有停下来时，我们就从服务器或者客户端的阻塞方法入手，解决出现的问题，这是最直接了当的解决方案。

需求4：用TcP协议通过多线程的方式将文件上传到服务器上

import java.util.*;
import java.net.*;
import java.io.*;
public class TcpDemo {

/**
*源：Socket读取流
*目的：Socket输出流
**/

public static void main(String[] args) throws Exception
{
ServerSocket ss = new ServerSocket(8001);
while(true)
{
Socket s = ss.accept();
new Thread(new MyThread(s)).start();
}

}

}
class ClientTcp{

public void sendFile(String[] args) throws Exception
{
Socket s = new Socket("192.168.0.149",8001);
File f = new File(args[0]);

InputStream is = new FileInputStream(f);
OutputStream os = s.getOutputStream();
int len = 0;
byte[] by = new byte[1024];
while((len=is.read(by))!=-1)
{
os.write(by,0,len);
}
s.shutdownOutput();
byte[] by1 = new byte[1024];
int arr = s.getInputStream().read(by1);
System.out.println(new String(by1,0,arr));
s.close();
}
public static void main(String[] args) throws Exception
{
ClientTcp td = new ClientTcp();
td.sendFile(args);
}

}

class MyThread implements Runnable
{
Socket s;
MyThread(Socket s)
{this.s=s;}
public void run()
{
try{

//获取连接客户端的ip地址
String ip = s.getInetAddress().getHostAddress();

System.out.println(ip+" 客户端连接上......");

InputStream is = s.getInputStream();
int count = 1;
File f1 = new File("d:\\"+ip+".jpg");
while(f1.exists())
f1 = new File("d:\\"+ip+"_("+(count++)+").jpg");

OutputStream os = new FileOutputStream(f1);
byte[] by = new byte[1024];
int len = 0;
while((len=is.read(by))!=-1)
{
os.write(by,0,len);
}

PrintWriter out = new PrintWriter(s.getOutputStream(),true);
out.println("上传成功");
}
catch(Exception e){}
}
}

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