Java网络编程初探
IP地址案例
package ch17;
import javax.swing.text.Style;
import java.net.InetAddress;
/**
* Created by Jiqing on 2017/1/5.
*/
public class InetAddressTest {
public static void main(String[] args) throws Exception{
InetAddress ip = InetAddress.getByName("www.baidu.com");
// 判断是否可达
System.out.println("百度是否可达:"+ip.isReachable(2000));
// 获取该实例的IP
System.out.println(ip.getHostAddress());
// 根据原始IP地址获取对应的InetAddress实例
InetAddress local = InetAddress.getByAddress(new byte[]{127,0,0,1});
System.out.println("本机是否可达："+local.isReachable(5000));
System.out.println(local.getCanonicalHostName());
}
}
结果：
百度是否可达:true
111.13.100.92
本机是否可达：true
127.0.0.1
下载图片案例
package ch17;
import java.io.InputStream;
import java.io.RandomAccessFile;
import java.net.HttpURLConnection;
import java.net.URL;
public class DownUtil
{
// 定义下载资源的路径
private String path;
// 指定所下载的文件的保存位置
private String targetFile;
// 定义需要使用多少线程下载资源
private int threadNum;
// 定义下载的线程对象
private DownThread[] threads;
// 定义下载的文件的总大小
private int fileSize;
public DownUtil(String path, String targetFile, int threadNum)
{
this.path = path;
this.threadNum = threadNum;
// 初始化threads数组
threads = new DownThread[threadNum];
this.targetFile = targetFile;
}
public void download() throws Exception
{
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
conn.setConnectTimeout(5 * 1000);
conn.setRequestMethod("GET");
conn.setRequestProperty(
"Accept",
"image/gif, image/jpeg, image/pjpeg, image/pjpeg, "
+ "application/x-shockwave-flash, application/xaml+xml, "
+ "application/vnd.ms-xpsdocument, application/x-ms-xbap, "
+ "application/x-ms-application, application/vnd.ms-excel, "
+ "application/vnd.ms-powerpoint, application/msword, */*");
conn.setRequestProperty("Accept-Language", "zh-CN");
conn.setRequestProperty("Charset", "UTF-8");
conn.setRequestProperty("Connection", "Keep-Alive");
// 得到文件大小
fileSize = conn.getContentLength();
conn.disconnect();
int currentPartSize = fileSize / threadNum + 1;//这里不必一定要加1,不加1也可以
RandomAccessFile file = new RandomAccessFile(targetFile, "rw");
// 设置本地文件的大小
file.setLength(fileSize);
file.close();
for (int i = 0; i < threadNum; i++)
{
// 计算每条线程的下载的开始位置
int startPos = i * currentPartSize;
// 每个线程使用一个RandomAccessFile进行下载
RandomAccessFile currentPart = new RandomAccessFile(targetFile, "rw");
// 定位该线程的下载位置
currentPart.seek(startPos);
// 创建下载线程
threads[i] = new DownThread(startPos, currentPartSize, currentPart);
// 启动下载线程
threads[i].start();
}
}
// 获取下载的完成百分比
public double getCompleteRate()
{
// 统计多条线程已经下载的总大小
int sumSize = 0;
for (int i = 0; i < threadNum; i++)
{
sumSize += threads[i].length;
}
// 返回已经完成的百分比
return sumSize * 1.0 / fileSize;
}
private class DownThread extends Thread
{
// 当前线程的下载位置
private int startPos;
// 定义当前线程负责下载的文件大小
private int currentPartSize;
// 当前线程需要下载的文件块
private RandomAccessFile currentPart;
// 定义已经该线程已下载的字节数
public int length;
public DownThread(int startPos, int currentPartSize,RandomAccessFile currentPart)
{
this.startPos = startPos;
this.currentPartSize = currentPartSize;
this.currentPart = currentPart;
}
@Override
public void run()
{
try
{
URL url = new URL(path);
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
conn.setConnectTimeout(5 * 1000);
conn.setRequestMethod("GET");
conn.setRequestProperty(
"Accept",
"image/gif, image/jpeg, image/pjpeg, image/pjpeg, "
+ "application/x-shockwave-flash, application/xaml+xml, "
+ "application/vnd.ms-xpsdocument, application/x-ms-xbap, "
+ "application/x-ms-application, application/vnd.ms-excel, "
+ "application/vnd.ms-powerpoint, application/msword, */*");
conn.setRequestProperty("Accept-Language", "zh-CN");
conn.setRequestProperty("Charset", "UTF-8");
InputStream inStream = conn.getInputStream();
// 跳过startPos个字节，表明该线程只下载自己负责哪部分文件。
inStream.skip(this.startPos);
byte[] buffer = new byte[1024];
int hasRead = 0;
// 读取网络数据，并写入本地文件
while (length < currentPartSize
&& (hasRead = inStream.read(buffer)) != -1)
{
currentPart.write(buffer, 0, hasRead);
// 累计该线程下载的总大小
length += hasRead;
}
currentPart.close();
inStream.close();
}
catch (Exception e)
{
e.printStackTrace();
}
}
}
}
package ch17;
import java.net.*;
/**
* Created by Jiqing on 2017/1/5.
*/
public class MultiThreadDown {
public static void main(String[] args) throws Exception{
// 初始化DownUtil对象
final DownUtil downUtil = new DownUtil("http://imgs.aixifan.com/live/1482830873793/1482830873793.jpg","demo.jpg",4);
// 开始下载
downUtil.download();
new Thread(() -> {
while(downUtil.getCompleteRate() < 1) {
// 每隔0.01秒查询一次任务完成进度
System.out.println("已完成："+ downUtil.getCompleteRate());
try {
Thread.sleep(10);
}catch (Exception ex) {}
}
}).start();
}
}
结果：
已完成：0.0
已完成：0.04389803969303463
已完成：0.09210067667384099
已完成：0.16440463214505055
已完成：0.39150257003269945
已完成：0.7543834411326956
已完成：0.9892219080763762
socket案例
服务端
package ch17;
import com.sun.xml.internal.ws.policy.privateutil.PolicyUtils;
import java.io.IOException;
import java.io.PrintStream;
import java.net.ServerSocket;
import java.net.Socket;
/**
* Created by Jiqing on 2017/1/6.
*/
public class Server {
public static void main(String[] args) throws IOException{
// 创建一个ServerSocket
ServerSocket ss = new ServerSocket(10000);
// 采用循环不断地接收来自客户端的请求
while(true) {
// 每当客户端Socket请求时，服务器端也产生一个socket
Socket s = ss.accept();
PrintStream ps = new PrintStream(s.getOutputStream());
ps.println("服务器的新年祝福！");
ps.close();
s.close();
}
}
}
客户端
package ch17;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;
/**
* Created by Jiqing on 2017/1/6.
*/
public class Client {
public static void main(String[] args) throws IOException{
Socket socket = new Socket("127.0.0.1",10000);
BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
String line = br.readLine();
System.out.println("来自服务器的数据："+line);
br.close();
socket.close();
}
}
通过ip+端口号进行数据传输。先运行服务器端，再运行客户端。
结果：
来自服务器的数据：服务器的新年祝福！
