CS Program 3 UDP Ping Server and Client Solution

Description

Program Submission: submit all the source code (*.java) to Canvas.

Program Description

You will develop a simple Internet Ping Server and a corresponding Client. The functionality provided by the Client and Server are similar to the standard ping programs available in modern operating systems. However, your Client and Server will be using UDP (instead of ICMP) to communicate with each other. The Server sits in an infinite loop listening for incoming UDP packets. When a packet comes in, the Server simply retrieves the payload, encapsulates the payload in an UDP packet, and sends the packet back to the Client. In other words, the Server is echoing the Client’s message. In this case, your Client is a Pinger. It must send 10 ping messages (UDP packets) consecutively to the Server and record the RTT (round-trip time) when the Server echoes back the UDP packet. You MUST use an UDP packet size of 512 bytes. The Client must output the minimum RTT, maximum RTT, and the average RTT at the end of program execution. I have a server running at constance.cs.rutgers.edu, 5530 for you to test your client (the pinger.)

The Ping Server

You must have a PingServer class providing UDP service. You can use any port number between 5520 and 5540 to receive the UDP packets. The Server MUST inject artificial loss to simulate the effects of network packet loss. That is, you must define a constant LOSS_RATE = 0.3 that determines the percentage of packets should be lost, and a constant AVERAGE_DELAY = 100 (milliseconds) to simulate transmission delay. Set AVERAGE_DELAY = 0 to find out the true RTT of your packets. Here are some useful methods:

//generate a random number between 0 and 1; it’s a packet loss if the random number is //less than LOSS_RATE

Random random = new Random(new Date().getTime());

//create the socket for receiving UDP packets

DatagramSocket udpSocket = new DatagramSocket(PORT_NUMBER);

//allocate the memory space for an UDP packet

byte[] buff = new byte[PACKET_SIZE];

//make an empty UDP packet

DatagramPacket inpacket = new DatagramPacket(buff, PACKET_SIZE);

//receive the next UDP packet

udpSocket.receive(inpacket);

//simulate transmission delay; DOUBLE = 2

Thread.sleep((int)(random.nextDouble() * DOUBLE * AVERAGE_DELAY));

//make an outgoing UDP packet

DatagramPacket outpacket =

new DatagramPacket(payload, payload.length, clientAddr, clientPort);

//send an UDP packet

udpSocket.send(outpacket);

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CS 352 Fall 2019 Dr. Lily Chang

The Client

Your Client should send 10 ping messages to the Server, with an one second (1000 milliseconds) interval. Each message contains a payload of data that includes the keyword PING, a sequence number, and a timestamp. After sending each packet, the client waits up to one second to receive a reply. If one second goes by without a reply from the server, then the client assumes that its packet or the server’s reply packet has been lost in the network. And the Client prints an error message identifying packet loss to the system output. You will need setSoTimeout() method in DatagramSocket class to set the timeout value on a datagram socket. Set 5 second timeout (5000 milliseconds) for collecting pings after 10 pings were sent, just to wait for possible delayed replies from the Server. You may include a PingClient class, a PingMessage class, and an UDPPinger class.

• PingMessage class

Use this class to create a ping message to be sent to the Server. The format of a ping message is shown below. You must provide the following public methods.

public PingMessage(InetAddress addr, int port, String payload) //constructor

public InetAddress getIP()		//get the destination IP address
public int getPort() //get		the destination port number
public String getPayload()		//get the content of the payload
	Destination IP address		Destination Port Number	Payload

The payload part of each PING message is a String with the following format. You can use the getTime() method in Date class to get the current time as the timestamp.

PING SPACE Sequence Number SPACE timestamp

• UDPPinger class

Use an instance of this class to send a ping message and receive the echo message from the Server. You must provide 2 public methods. You may need .getAddress(), .getData() and .getPort() in

DatagramPacket class.

/**

This method sends an UDP packet with an instance of PingMessage.

Use the constructor

DatagramPacket(byte[] payload, int length, InetAddress address, int port) to construct an UDP packet and send the UDP packet.

*/

public void sendPing(PingMessage ping)

//This method receives the UDP packet from the Server. This method may throw

• SocketTimeoutException. public PingMessage receivePing()

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CS 352 Fall 2019 Dr. Lily Chang

• PingClient class

This is the Client class.This class extends UDPPinger class, and implements the Java Runnable interface. That is, you MUST implement the run() method. In the run() method, you MUST

• 1. Create an instance of DatagramSocket.

• 2. Set the time out for the socket to be 1 second (1000 milliseconds)

• 3. Set up a for loop to send 10 PING messages, record the replies from the Server, and compute the RTT.

  4. Wait additional 5 seconds (set time out to 5 seconds) after 10 PINGs are sent (if less than 10 replies are received), just in case replies are on the way.

• 5. Compute and output the average RTT, minimum and maximum RTTs. Use the following formula. Set the RTT to 1000 milliseconds in case of a packet loss.

RTT = (current timestamp) – (previous timestamp when sending the packet)

Program Requirement

1. Your programs MUST NOT crash under any situation.

2. You MUST try-catch everything and display appropriate error messages identifying the specific exception.

3. You MUST display information about ping messages on Server’s system output, and on Client’s system output.

Sample output for the Server

Ping Server running….

Waiting for UDP packet….

Received from: /127.0.0.1 PING 0 1572707989954

Packet loss…., reply not sent.

Waiting for UDP packet….

Received from: /127.0.0.1 PING 1 1572707990988

Reply sent.

Waiting for UDP packet….

Received from: /127.0.0.1 PING 2 1572707991636

Packet loss…., reply not sent.

Waiting for UDP packet….

Received from: /127.0.0.1 PING 3 1572707992637

Reply sent.

Waiting for UDP packet….

Received from: /127.0.0.1 PING 4 1572707992660

Reply sent.

Waiting for UDP packet….

Received from: /127.0.0.1 PING 5 1572707992981

Packet loss…., reply not sent.

Waiting for UDP packet….

Received from: /127.0.0.1 PING 6 1572707993983

Reply sent.

Waiting for UDP packet….

Received from: /127.0.0.1 PING 7 1572707994937

Packet loss…., reply not sent.

Waiting for UDP packet….

Received from: /127.0.0.1 PING 8 1572707995938

Reply sent.

Waiting for UDP packet….

Received from: /127.0.0.1 PING 9 1572707996880

Reply sent.

Waiting for UDP packet….

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