client.java

Icarnegie university SSD8电子书和全部练习答案

/**
* @author lu hongyong 043742
* @see <code>Server.java</code>
* @version 1.0
* 
* The file is to build a Simple HTTP/1.0 Client with a Command Line Interface.
*
*/

import java.net.*;
import java.io.*;


public class Client {

// The port number in static final type . 
private static final int socketPort = 6789;

// Default constructor.
public Client() {}

/**
* This method is used to send the client's request to the server.
* 
* @param <code>Socket</code>object and <code>String</code> message object.
* @return void.
* @exception <code>IOException</code>.
*/
public void sendMessage(Socket clientSocket, String message) {

String clientRequest;
System.out.println(message + " is listening to your request:\n");

BufferedReader inFromClient = new BufferedReader(new InputStreamReader(System.in));

// In "Try-Catch" block, we do the actual work to send the message out, 
// and when the IO erro countered, throw out "IOException". 
try {

DataOutputStream outToServer = new DataOutputStream(clientSocket.getOutputStream());
clientRequest = inFromClient.readLine();
outToServer.writeBytes(clientRequest + "\r\n\r\n");

} catch (IOException ioe) {

System.err.println("IO erro: ");
ioe.printStackTrace();
}

}

/**
* The method header is used to get the header out from the server reply, and print it out to the console.
* 
* @param <code>InputStream</code>
* @return void
* @exception <code>IOException</code>
* 
*/ 
public void header(InputStream inFromServer) {

String header = "";
int temp;
boolean isHeader = false;

try {
temp = inFromServer.read();
System.out.println(temp);
header += (char) temp;

// When the string is "\r\n\r\n", the header is over, and we get it.
while (temp != -1 && !isHeader) {
switch (temp) {
case 13:
temp = inFromServer.read();
switch (temp) {
case 10:
header += (char) temp;
if ((char) (temp = inFromServer.read()) == ('\r'))
if ((char) (temp = inFromServer.read()) == ('\n'))
isHeader = true;
break;
default:
break;
}
break;
default:
break;
}
if (isHeader)
break;
temp = inFromServer.read();
header += (char) temp;
}

} catch (IOException ioe) {

System.err.println("IO erro: ");
ioe.printStackTrace();
}

System.out.println("header:\n" + header + "\n");
}

/**
* This method is used to change the flow that come from server to the type of "byte".
* 
* @param <code>InputStream</code> object and <code>Socket</code> object.
* @return <code>byte[]</code>
* @exception <code>EOFException</code> and <code>IOException</code>
*/
public byte[] serverReply(InputStream inFromServer, Socket clientSocket) {

int fileLength=0;
byte[] buffer = null;

// Get the length of the flow that come from the server and it may cause the IOException.
try {

fileLength = inFromServer.available();
} catch (IOException e) {

System.err.println("IO erro when \"inFromServer.available()\" ");
e.printStackTrace();
}

buffer = new byte[fileLength];
DataInputStream receivedFile = null; 

receivedFile = new DataInputStream(inFromServer);

// Get every byte from the DataInputStream object to the buffer array.
try {

for (int i=0;i<buffer.length;i++){
buffer[i] = receivedFile.readByte();
}
} catch (EOFException eof) {

eof.printStackTrace();
}catch (IOException e2) {

e2.printStackTrace();
} 

return buffer;
}

/**
* This method is used to save the infomation from server to the local file.
* 
* @param <code>BufferedReader</code> object and <code>byte[]</code> object.
* @return void.
* @exception <code>FileNotFoundException</code> and <code>IOException</code>.
*/
public void saveFile(BufferedReader inFromClient, byte[] buffer) {

System.out.println("Input a file name to save the header:\n");

// Write the infomation to the file whose name is inputed by the user.
try {

FileOutputStream fileout = new FileOutputStream(inFromClient.readLine());
PrintStream ps = new PrintStream(fileout);
ps.write(buffer);
ps.close();

} catch (FileNotFoundException fnfe) {

System.err.println("The specified file is not exist!");
fnfe.printStackTrace();

} catch (IOException ioe) {

System.err.println("IO erro: ");
ioe.printStackTrace();
}
}


public static void main(String[] args) throws Exception {

// Creat a new Client object.
Client client = new Client();
Socket clientSocket = null;

// Establish a socket connection.
try {

clientSocket = new Socket(args[0], socketPort);
} catch (UnknownHostException unke) {

System.err.println("The host is unknown!");
unke.printStackTrace();

} catch (IOException ioe) {

System.err.println("IO erro: ");
ioe.printStackTrace();
} catch (SecurityException se) {

System.err.println("A security manager exists and we cannot get throw it.");
se.printStackTrace();
}

BufferedReader inFromClient = new BufferedReader(new InputStreamReader(
System.in, "UTF-8"));

InputStream inFromServer = new BufferedInputStream(clientSocket.getInputStream());


client.sendMessage(clientSocket, args[0]); //Send message.
client.header(inFromServer); //Get header.
byte[] buffer = client.serverReply(inFromServer, clientSocket); //Change the stream flow to the type of "byte"
client.saveFile(inFromClient, buffer); //Save file
clientSocket.close(); //Close the connection.

}

}