java socket联接c/s (转)
java socket连接c/s (转)
java socket连接c/s (转)
2010年07月08日
用java实现的简单Server/Client文件传输关键字: java server client
用一种编程语言实现一个简单的Server/Client程序; 该程序的主要功能是利用Client从Server端下载一个文件; 在下载之前,需要有一定的用户身份验证机制(说白了就是先输入以下用户名和密码); Server应该是多线程机制的,即为每个Client请求Server都要有一个线程去处理,而不是所有的Client都是一个Server线程处理。 ok,这就是需求,单从编程角度来讲,题目不难,单老师说过一句话,我觉得非常有道理,“看一万个程序,不如自己亲自写一个程序,写一万个程序,不如努力写一个好程序”,所以我就利用十一假期的最后两天,完成了这样一个作业,当然大部分时间还是画在了学习不太熟悉的python上。在这里,还要感谢一下CSDN上“wumingabc的专栏”的一篇blog,参考了他的一些代码。
处理流程:
server启动,监听client请求; client启动; server监听到client,发送“Hi”; client收到“Hi” client要求用户输入用户名; 用户输入用户名(如yangsq),发送到服务器(形式为“username:yangsq”); 服务器验证是否存在这样一个用户,如果有到step 8,否则转到5; client用求用户输入密码(如123456),发送到服务器(形式为“password:123456”); 服务器验证密码是否正确,不正确转到step 8,正确开始传输文件(为了简单,文件预先指定好); client收到文件,结束后发送“bye”;同时server端收到“bye”后结束线程。 服务器端:
java 代码
import java.io.BufferedOutputStream; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.OutputStreamWriter; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; import java.util.HashMap; import java.util.Map; public class SimpleServer extends Thread{ private static final int DEFAULT_PORT = 4444; private static final String DEFAULT_FILE_NAME = "PyNet.pdf"; private Socket socket; public SimpleServer(Socket socket){ this.socket = socket; start(); } @Override public void run() { System.out.println("Connected from " + socket.getRemoteSocketAddress()); try { BufferedReader in = new BufferedReader( new InputStreamReader(socket.getInputStream())); PrintWriter out = new PrintWriter( new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true); String inputLine, outputLine; HandleInput handleInput = new HandleInput(); outputLine = handleInput.handle(null); out.println(outputLine); while((inputLine = in.readLine()) != null){ outputLine = handleInput.handle(inputLine); out.println(outputLine); out.flush(); if(outputLine.equals("bye")) break; if(outputLine.equals("password:valid")){ //prepare for the transmission of the file Thread.sleep(2000); InputStream fileInput = new FileInputStream(new File(DEFAULT_FILE_NAME)); OutputStream fileOutput = new DataOutputStream( new BufferedOutputStream(socket.getOutputStream())); byte[] buf = new byte[2048]; //transmit the file int num = fileInput.read(buf); while(num != -1){ fileOutput.write(buf, 0, num); fileOutput.flush(); num = fileInput.read(buf); } fileInput.close(); fileOutput.close(); } } in.close(); out.close(); System.out.println("Disconnected from " + socket.getRemoteSocketAddress()); socket.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } private class HandleInput{ private Map userInfo = new HashMap(); private String username = ""; private String password = ""; public HandleInput(){ userInfo.put("yangsq", "yangsq"); userInfo.put("abc", "abc"); userInfo.put("123", "123"); } public String handle(String input){ String output = ""; if(input == null) output = "Hi"; else if(input.startsWith("username")){ username = input.split(":")[1]; if(userInfo.containsKey(username)) output = "username:valid"; else output = "username:invalid"; }else if(input.startsWith("password")){ password = input.split(":")[1]; if(userInfo.get(username).equals(password)) output = "password:valid"; else output = "password:invalid"; }else if(input.equals("bye")){ output = "bye"; } return output; } } public static void main(String[] args) { int port = DEFAULT_PORT; if(args.length > 0){ port = Integer.parseInt(args[0]); } try { ServerSocket serverSocket = new ServerSocket(port); System.out.println("Server Started"); try { while(true){ Socket theSocket = serverSocket.accept(); try { new SimpleServer(theSocket); } catch (Exception e) { e.printStackTrace(); theSocket.close(); } } } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } finally { if(serverSocket != null) serverSocket.close(); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }
说明:
main函数是Server的启动点,在这里我们建立了一个ServerSocket的实例,这个类是java中专门进行Server端编程的,它可以进行很多的复杂配置,这里知识把它建立在了一个端口之上(line-125),然后为请求返回socket(line-131)。 SimpleServer类继承了Thread,也就是说,我的想法是为每一个Client请求,都有一个SimpleServer去处理。这是怎样实现的呢?看line-128到line-136,这里ServerSocket的实例在端口4444进行监听,只要有一个请求,就new一个SimpleServer去处理(如果没有请求,程序就会阻塞在ServerSocket的accept方法上line-129) 既然SimpleServer继承了Thread,那么它的最重要的方法就是run(line-29),可以看到,在new SimpleServer的时候就启动了它的run方法。 SimpleServer的主要处理流程在line-42到line-67,为了更清晰,把其中的用户身份验证提出来组成一个内部类HandleInput。 负责文件传输的是line-48到line-66,也即clien的密码正确后开始。这里需要说明的是流的实现,与用户交互的时候我们用的是New IO,他们是面向字节(1字节=2byte)的,这很合适,因为我们的用户信息都是字节的(简单的说就是面向asc字符的),所以这里我们就用了readline和println方法(这两个都是Reader和Writer的方法);但是我们要传输的是一个二进制文件(说白了就是面向byte的),所以用New IO就不合适了,所以转向了InputStream(读入文件)和OutputStream(把文件通过socket写出)。 客户端:
java 代码
import java.io.BufferedInputStream; import java.io.BufferedReader; import java.io.DataInputStream; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.PrintWriter; import java.io.RandomAccessFile; import java.net.Socket; import java.net.UnknownHostException; public class SimpleClient { private static final int DEFAULT_PORT = 4444; private static final String DEFAULT_HOST = "localhost"; public static void main(String[] args) { String host = DEFAULT_HOST; int port = DEFAULT_PORT; if(args.length > 0){ host = args[0]; } if(args.length >1 ){ port = Integer.parseInt(args[1]); } Socket theSocket = null; PrintWriter out = null; BufferedReader in = null, userIn = null; try { theSocket = new Socket(host, port); in = new BufferedReader( new InputStreamReader(theSocket.getInputStream())); out = new PrintWriter(theSocket.getOutputStream()); userIn = new BufferedReader( new InputStreamReader(System.in)); System.out.println("Connected to the simple file server"); String fromUser, fromServer; while((fromServer = in.readLine()) != null){ if(fromServer.equals("bye")) break; else if(fromServer.equals("Hi")){ System.out.println("Do you want to get the 'PyNet.pdf' file?(y/n):"); fromUser = userIn.readLine(); if(fromUser.equals("y")){ System.out.println("Please input your username:"); fromUser = userIn.readLine(); out.println("username:" + fromUser); out.flush();//notice: if this sentence is lost, the info will not arrive at server side }else break; }else if(fromServer.startsWith("username")){ if(fromServer.split(":")[1].equals("valid")){ System.out.println("Please input your password:"); fromUser = userIn.readLine(); out.println("password:" + fromUser); out.flush(); }else{ System.out.println("Please input your username:"); fromUser = userIn.readLine(); out.println("username:" + fromUser); out.flush(); } }else if(fromServer.startsWith("password")){ if(fromServer.split(":")[1].equals("valid")){ System.out.println("Downloading..."); //prepare for the receiving File newFile = new File("new.pdf"); newFile.createNewFile(); RandomAccessFile raf = new RandomAccessFile(newFile, "rw"); InputStream fileInput = new DataInputStream( new BufferedInputStream(theSocket.getInputStream())); byte[] buf = new byte[2048]; //receiving int num = fileInput.read(buf); while(num != -1){ raf.write(buf, 0, num); raf.skipBytes(num); num = fileInput.read(buf); } in.close(); raf.close(); System.out.println("File download is finished"); break; }else{ System.out.println("Please input your password:"); fromUser = userIn.readLine(); out.println("password:" + fromUser); out.flush(); } } } out.println("bye"); out.flush(); out.close(); in.close(); userIn.close(); theSocket.close(); } catch (UnknownHostException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }
这个比较简单,除了用户交互外,最核心的就是line-71到line-94这段处理文件下载的了,当SimpleClient收到服务器的“password:valid"就表示用户身份验证通过,可以执行文件下载了。这部分也是混合使用了New IO和Old IO,原因和上边解释的一样。
这里还要强调一点的是在网络编程的时候,println以后,一定要flush以下。为什么呢?学过网络的人都知道,当一个package太小是,网络并不会把它发出去,而是等到足够大时。我在实际测试时,就忘记了在println后写flush,结果这边明明已经out出了,但Server端就是在那塞着,这个问题困扰了我半天,呵呵。
java socket连接c/s (转)
2010年07月08日
用java实现的简单Server/Client文件传输关键字: java server client
用一种编程语言实现一个简单的Server/Client程序; 该程序的主要功能是利用Client从Server端下载一个文件; 在下载之前,需要有一定的用户身份验证机制(说白了就是先输入以下用户名和密码); Server应该是多线程机制的,即为每个Client请求Server都要有一个线程去处理,而不是所有的Client都是一个Server线程处理。 ok,这就是需求,单从编程角度来讲,题目不难,单老师说过一句话,我觉得非常有道理,“看一万个程序,不如自己亲自写一个程序,写一万个程序,不如努力写一个好程序”,所以我就利用十一假期的最后两天,完成了这样一个作业,当然大部分时间还是画在了学习不太熟悉的python上。在这里,还要感谢一下CSDN上“wumingabc的专栏”的一篇blog,参考了他的一些代码。
处理流程:
server启动,监听client请求; client启动; server监听到client,发送“Hi”; client收到“Hi” client要求用户输入用户名; 用户输入用户名(如yangsq),发送到服务器(形式为“username:yangsq”); 服务器验证是否存在这样一个用户,如果有到step 8,否则转到5; client用求用户输入密码(如123456),发送到服务器(形式为“password:123456”); 服务器验证密码是否正确,不正确转到step 8,正确开始传输文件(为了简单,文件预先指定好); client收到文件,结束后发送“bye”;同时server端收到“bye”后结束线程。 服务器端:
java 代码
import java.io.BufferedOutputStream; import java.io.BufferedReader; import java.io.BufferedWriter; import java.io.DataOutputStream; import java.io.File; import java.io.FileInputStream; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.OutputStream; import java.io.OutputStreamWriter; import java.io.PrintWriter; import java.net.ServerSocket; import java.net.Socket; import java.util.HashMap; import java.util.Map; public class SimpleServer extends Thread{ private static final int DEFAULT_PORT = 4444; private static final String DEFAULT_FILE_NAME = "PyNet.pdf"; private Socket socket; public SimpleServer(Socket socket){ this.socket = socket; start(); } @Override public void run() { System.out.println("Connected from " + socket.getRemoteSocketAddress()); try { BufferedReader in = new BufferedReader( new InputStreamReader(socket.getInputStream())); PrintWriter out = new PrintWriter( new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())), true); String inputLine, outputLine; HandleInput handleInput = new HandleInput(); outputLine = handleInput.handle(null); out.println(outputLine); while((inputLine = in.readLine()) != null){ outputLine = handleInput.handle(inputLine); out.println(outputLine); out.flush(); if(outputLine.equals("bye")) break; if(outputLine.equals("password:valid")){ //prepare for the transmission of the file Thread.sleep(2000); InputStream fileInput = new FileInputStream(new File(DEFAULT_FILE_NAME)); OutputStream fileOutput = new DataOutputStream( new BufferedOutputStream(socket.getOutputStream())); byte[] buf = new byte[2048]; //transmit the file int num = fileInput.read(buf); while(num != -1){ fileOutput.write(buf, 0, num); fileOutput.flush(); num = fileInput.read(buf); } fileInput.close(); fileOutput.close(); } } in.close(); out.close(); System.out.println("Disconnected from " + socket.getRemoteSocketAddress()); socket.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } } private class HandleInput{ private Map userInfo = new HashMap(); private String username = ""; private String password = ""; public HandleInput(){ userInfo.put("yangsq", "yangsq"); userInfo.put("abc", "abc"); userInfo.put("123", "123"); } public String handle(String input){ String output = ""; if(input == null) output = "Hi"; else if(input.startsWith("username")){ username = input.split(":")[1]; if(userInfo.containsKey(username)) output = "username:valid"; else output = "username:invalid"; }else if(input.startsWith("password")){ password = input.split(":")[1]; if(userInfo.get(username).equals(password)) output = "password:valid"; else output = "password:invalid"; }else if(input.equals("bye")){ output = "bye"; } return output; } } public static void main(String[] args) { int port = DEFAULT_PORT; if(args.length > 0){ port = Integer.parseInt(args[0]); } try { ServerSocket serverSocket = new ServerSocket(port); System.out.println("Server Started"); try { while(true){ Socket theSocket = serverSocket.accept(); try { new SimpleServer(theSocket); } catch (Exception e) { e.printStackTrace(); theSocket.close(); } } } catch (Exception e) { // TODO: handle exception e.printStackTrace(); } finally { if(serverSocket != null) serverSocket.close(); } } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }
说明:
main函数是Server的启动点,在这里我们建立了一个ServerSocket的实例,这个类是java中专门进行Server端编程的,它可以进行很多的复杂配置,这里知识把它建立在了一个端口之上(line-125),然后为请求返回socket(line-131)。 SimpleServer类继承了Thread,也就是说,我的想法是为每一个Client请求,都有一个SimpleServer去处理。这是怎样实现的呢?看line-128到line-136,这里ServerSocket的实例在端口4444进行监听,只要有一个请求,就new一个SimpleServer去处理(如果没有请求,程序就会阻塞在ServerSocket的accept方法上line-129) 既然SimpleServer继承了Thread,那么它的最重要的方法就是run(line-29),可以看到,在new SimpleServer的时候就启动了它的run方法。 SimpleServer的主要处理流程在line-42到line-67,为了更清晰,把其中的用户身份验证提出来组成一个内部类HandleInput。 负责文件传输的是line-48到line-66,也即clien的密码正确后开始。这里需要说明的是流的实现,与用户交互的时候我们用的是New IO,他们是面向字节(1字节=2byte)的,这很合适,因为我们的用户信息都是字节的(简单的说就是面向asc字符的),所以这里我们就用了readline和println方法(这两个都是Reader和Writer的方法);但是我们要传输的是一个二进制文件(说白了就是面向byte的),所以用New IO就不合适了,所以转向了InputStream(读入文件)和OutputStream(把文件通过socket写出)。 客户端:
java 代码
import java.io.BufferedInputStream; import java.io.BufferedReader; import java.io.DataInputStream; import java.io.File; import java.io.IOException; import java.io.InputStream; import java.io.InputStreamReader; import java.io.PrintWriter; import java.io.RandomAccessFile; import java.net.Socket; import java.net.UnknownHostException; public class SimpleClient { private static final int DEFAULT_PORT = 4444; private static final String DEFAULT_HOST = "localhost"; public static void main(String[] args) { String host = DEFAULT_HOST; int port = DEFAULT_PORT; if(args.length > 0){ host = args[0]; } if(args.length >1 ){ port = Integer.parseInt(args[1]); } Socket theSocket = null; PrintWriter out = null; BufferedReader in = null, userIn = null; try { theSocket = new Socket(host, port); in = new BufferedReader( new InputStreamReader(theSocket.getInputStream())); out = new PrintWriter(theSocket.getOutputStream()); userIn = new BufferedReader( new InputStreamReader(System.in)); System.out.println("Connected to the simple file server"); String fromUser, fromServer; while((fromServer = in.readLine()) != null){ if(fromServer.equals("bye")) break; else if(fromServer.equals("Hi")){ System.out.println("Do you want to get the 'PyNet.pdf' file?(y/n):"); fromUser = userIn.readLine(); if(fromUser.equals("y")){ System.out.println("Please input your username:"); fromUser = userIn.readLine(); out.println("username:" + fromUser); out.flush();//notice: if this sentence is lost, the info will not arrive at server side }else break; }else if(fromServer.startsWith("username")){ if(fromServer.split(":")[1].equals("valid")){ System.out.println("Please input your password:"); fromUser = userIn.readLine(); out.println("password:" + fromUser); out.flush(); }else{ System.out.println("Please input your username:"); fromUser = userIn.readLine(); out.println("username:" + fromUser); out.flush(); } }else if(fromServer.startsWith("password")){ if(fromServer.split(":")[1].equals("valid")){ System.out.println("Downloading..."); //prepare for the receiving File newFile = new File("new.pdf"); newFile.createNewFile(); RandomAccessFile raf = new RandomAccessFile(newFile, "rw"); InputStream fileInput = new DataInputStream( new BufferedInputStream(theSocket.getInputStream())); byte[] buf = new byte[2048]; //receiving int num = fileInput.read(buf); while(num != -1){ raf.write(buf, 0, num); raf.skipBytes(num); num = fileInput.read(buf); } in.close(); raf.close(); System.out.println("File download is finished"); break; }else{ System.out.println("Please input your password:"); fromUser = userIn.readLine(); out.println("password:" + fromUser); out.flush(); } } } out.println("bye"); out.flush(); out.close(); in.close(); userIn.close(); theSocket.close(); } catch (UnknownHostException e) { // TODO Auto-generated catch block e.printStackTrace(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } }
这个比较简单,除了用户交互外,最核心的就是line-71到line-94这段处理文件下载的了,当SimpleClient收到服务器的“password:valid"就表示用户身份验证通过,可以执行文件下载了。这部分也是混合使用了New IO和Old IO,原因和上边解释的一样。
这里还要强调一点的是在网络编程的时候,println以后,一定要flush以下。为什么呢?学过网络的人都知道,当一个package太小是,网络并不会把它发出去,而是等到足够大时。我在实际测试时,就忘记了在println后写flush,结果这边明明已经out出了,但Server端就是在那塞着,这个问题困扰了我半天,呵呵。