I did not get the job after submitting this piece of work in an interview, but I have no feedback to know what "BAD" things are inside this block of code.
The requirements are:
- Connect to the server on a known port and IP
- Asynchronously send a message to the server in your choice of format
- Calculate and display the round trip time for each message and the average round trip time for all messages sent
The solution should not be so hard. But I just don't know what's wrong? Bad design? Bad naming? Bad practise?
import java.io.BufferedReader;
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.Socket;
import java.net.UnknownHostException;
public class EchoClient {
private String hostname;
private int port;
private Socket clientSocket;
private BufferedReader inFromUser, inFromServer;
private DataOutputStream outToServer;
private double averageTime = 0;
private int count = 0;
public EchoClient(String hostname, int port){
this.hostname = hostname;
this.port = port;
try {
this.clientSocket = new Socket(this.hostname, this.port);
} catch (UnknownHostException e) {
System.out.println("Connection Error: unknown host");
System.exit(1);
} catch (IOException e) {
System.out.println("Connection Error: connection refused");
System.exit(1);
}
try{
this.inFromUser = new BufferedReader( new InputStreamReader(System.in));
this.outToServer = new DataOutputStream(this.clientSocket.getOutputStream());
this.inFromServer = new BufferedReader(
new InputStreamReader(this.clientSocket.getInputStream()));
} catch (IOException e) {
System.out.println("Error on Initializing echoclient");
System.exit(1);
}
}
public void start(){
System.out.println("Connecting to " + hostname + " with port No " + port);
String msgSend;
try {
while ((msgSend = inFromUser.readLine()) != null){
// sendMessage asynchronous
sendMessage(msgSend, new Callback(){
// callback function and calculate the average time
public void callback(long timeUsed, String msgReceived){
averageTime = (count * averageTime + (timeUsed)) / (count + 1);
++count;
System.out.println(msgReceived +
" rtt=" + (double)Math.round(timeUsed * 100)/100 + " ms" +
" artt=" + (double)Math.round(averageTime * 100)/100 + " ms");
}
});
}
} catch (IOException e) {
System.out.println("Error on reading message from user");
}
}
private void sendMessage(String message, Callback cb){
Thread sendMessageThread = new Thread(new SendMessageRequest(message, cb));
sendMessageThread.start();
}
interface Callback {
public void callback(long time, String msg);
}
class SendMessageRequest implements Runnable{
private String message;
private Callback cb;
SendMessageRequest(String message, Callback cb){
this.message = message;
this.cb = cb;
}
@Override
public void run() {
String msgReceived;
long timeStart, timeEnd, timeUsed;
try {
timeStart = System.nanoTime();
outToServer.writeBytes(this.message + '\n');
msgReceived = inFromServer.readLine();
timeEnd = System.nanoTime();
// Calculate the time and get the output
timeUsed = (timeEnd - timeStart) / 1000000;
cb.callback(timeUsed, msgReceived);
} catch (IOException e) {
System.out.println("Error on sending message to server");
}
}
}
public static void showUsage(){
System.out.println("Usage: java EchoClient [hostname] [portNo]");
}
/**
* Entry of the program
*/
public static void main(String[] args) {
String hostname = "";
int port = 0;
if (args.length < 2){
showUsage();
System.exit(0);
}
else{
hostname = args[0];
port = Integer.parseInt(args[1]);
}
EchoClient client = new EchoClient(hostname, port);
client.start();
}
}
