Chapter 2 Application Layer: Socket Programming
Chapter 2
Application Layer:
Socket Programming
Jaringan Komputer
Jurusan Ilmu Komputer/ Informatika
Universitas Diponegoro
2012/2013
Computer Networking:
A Top Down Approach,
5th edition.
Jim Kurose, Keith Ross
Addison-Wesley, April
2009.
2: Application Layer
1
Network Applications
1.
Protocol standard defined RFC
RFC 959 FTP
2. Proprietary
single developer client-server
Not to use one of the well-known port numbers
defined in the RFC.
T C P or UDP ?
T C P connection oriented, reliable
UDP connectionless, unreliable
2: Application Layer
2
Example of
Client Server Communication
2: Application Layer
3
Socket programming
Goal: learn how to build client/server application that
communicate using sockets
Socket API
introduced in BSD4.1 UNIX,
1981
explicitly created, used,
released by apps
client/server paradigm
two types of transport
service via socket API:
UDP
TCP
socket
An application-created,
OS-controlled interface
(a “door”) into which
application process can
both send and
receive messages to/from
another application
process
2: Application Layer
4
Socket programming basics
Server must be
running before
client can send
anything to it.
Server must have a
socket (door)
through which it
receives and sends
segments
Similarly client
needs a socket
Socket is locally
identified with a port
number
Analogous to the apt #
in a building
Client needs to know
server IP address and
socket port number.
2: Application Layer
5
Chapter 2: Application layer
2.1 Principles of
2.6 P2P applications
network applications
2.2 Web and HTTP
2.3 FTP (skip)
2.4 Electronic Mail
(skip)
2.7 Socket programming
with TCP
2.8 Socket programming
with UDP
SMTP, POP3, IMAP
2.5 DNS
2: Application Layer
6
Socket-programming using TCP
TCP service: reliable transfer of bytes from one
process to another
controlled by
application
developer
controlled by
operating
system
process
process
socket
TCP with
buffers,
variables
socket
TCP with
buffers,
variables
host or
server
internet
controlled by
application
developer
controlled by
operating
system
host or
server
2: Application Layer
7
Socket programming with TCP
Client must contact server
server process must first
be running
server must have created
socket (door) that
welcomes client’s contact
Client contacts server by:
creating client-local TCP
socket
specifying IP address, port
number of server process
When client creates
socket: client TCP
establishes connection to
server TCP
When contacted by client,
server TCP creates new
socket for server process to
communicate with client
allows server to talk with
multiple clients
source port numbers
used to distinguish
clients (more in Chap 3)
application viewpoint
TCP provides reliable, in-order
transfer of bytes (“pipe”)
between client and server
2: Application Layer
8
Client Socket, Welcoming Socket,
and Connection Socket
2: Application Layer
9
Client/server socket interaction: TCP
Server (running on hostid)
Client
create socket,
port=x, for
incoming request:
welcomeSocket =
ServerSocket()
TCP
wait for incoming
connection request connection
connectionSocket =
welcomeSocket.accept()
read request from
connectionSocket
write reply to
connectionSocket
close
connectionSocket
setup
create socket,
connect to hostid, port=x
clientSocket =
Socket()
send request using
clientSocket
read reply from
clientSocket
close
clientSocket
2: Application Layer
10
Stream jargon
Client
Process
process
output
stream
monitor
inFromUser
input
stream
outToServer
characters that flow into or
out of a process.
An input stream is attached to
some input source for the
process, e.g., keyboard or
socket.
An output stream is attached
to an output source, e.g.,
monitor or socket.
The DataOutputStream class
has some methods to convert
(and send out) data into any
primitif data type, depend on
our need; Such as byte,
integer, char, etc
keyboard
inFromServer
A stream is a sequence of
input
stream
client
TCP
clientSocket
socket
to network
TCP
socket
from network
2: Application Layer
11
Socket programming with TCP
Example client-server app:
1) client reads line from
standard input (inFromUser
stream) , sends to server via
socket (outToServer
stream)
2) server reads line from socket
3) server converts line to
uppercase,
4) Server sends back to client
4) client reads, prints modified
line from socket
(inFromServer stream)
2: Application Layer
12
Example: Java client (TCP)
import java.io.*;
import java.net.*;
class TCPClient {
public static void main(String argv[]) throws Exception
{
String sentence;
String modifiedSentence;
Create
input stream
Create
client socket,
connect to server
Create
output stream
attached to socket
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
Socket clientSocket = new Socket("hostname", 6789);
DataOutputStream outToServer =
new DataOutputStream(clientSocket.getOutputStream());
2: Application Layer
13
Example: Java client (TCP), cont.
Create
input stream
attached to socket
BufferedReader inFromServer =
new BufferedReader(new
InputStreamReader(clientSocket.getInputStream()));
sentence = inFromUser.readLine();
Send line
to server
outToServer.writeBytes(sentence + '\n');
modifiedSentence = inFromServer.readLine();
Read line
from server
System.out.println("FROM SERVER: " + modifiedSentence);
clientSocket.close();
}
}
2: Application Layer
14
Example: Java server (TCP)
import java.io.*;
import java.net.*;
class TCPServer {
Create
welcoming socket
at port 6789
Wait, on welcoming
socket for contact
by client
Create input
stream, attached
to socket
public static void main(String argv[]) throws Exception
{
String clientSentence;
String capitalizedSentence;
ServerSocket welcomeSocket = new ServerSocket(6789);
while(true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient =
new BufferedReader(new
InputStreamReader(connectionSocket.getInputStream()));
2: Application Layer
15
Example: Java server (TCP), cont
Create output
stream, attached
to socket
DataOutputStream outToClient =
new DataOutputStream(connectionSocket.getOutputStream());
Read in line
from socket
clientSentence = inFromClient.readLine();
capitalizedSentence = clientSentence.toUpperCase() + '\n';
Write out line
to socket
outToClient.writeBytes(capitalizedSentence);
}
}
}
End of while loop,
loop back and wait for
another client connection
2: Application Layer
16
TCP observations & questions
Server has two types of sockets:
ServerSocket and Socket
When client knocks on serverSocket’s “door,”
server creates connectionSocket and completes
TCP conx.
Dest IP and port are not explicitly attached to
segment.
Can multiple clients use the server?
2: Application Layer
17
Chapter 2: Application layer
2.1 Principles of
2.6 P2P applications
network applications
2.2 Web and HTTP
2.3 FTP (skip)
2.4 Electronic Mail
(skip)
2.7 Socket programming
with TCP
2.8 Socket programming
with UDP
SMTP, POP3, IMAP
2.5 DNS
2: Application Layer
18
Socket programming with UDP
UDP: no “connection” between
client and server
no handshaking
sender explicitly attaches
IP address and port of
destination to each segment
OS attaches IP address and
port of sending socket to
each segment
Server can extract IP
address, port of sender
from received segment
application viewpoint
UDP provides unreliable transfer
of groups of bytes (“datagrams”)
between client and server
Note: the official terminology
for a UDP packet is “datagram”.
In this class, we instead use “UDP
segment”.
2: Application Layer
19
Running example
Client:
User types line of text
Client program sends line to server
Server:
Server receives line of text
Capitalizes all the letters
Sends modified line to client
Client:
Receives line of text
Displays
2: Application Layer
20
Client/server socket interaction: UDP
Server (running on hostid)
create socket,
port= x.
serverSocket =
DatagramSocket()
read datagram from
serverSocket
write reply to
serverSocket
specifying
client address,
port number
Client
create socket,
clientSocket =
DatagramSocket()
Create datagram with server IP and
port=x; send datagram via
clientSocket
read datagram from
clientSocket
close
clientSocket
2: Application Layer
21
Example: Java client (UDP)
input
stream
Client
process
monitor
inFromUser
keyboard
Process
Input: receives
packet (recall
thatTCP received
“byte stream”)
UDP
packet
receivePacket
packet (recall
that TCP sent
“byte stream”)
sendPacket
Output: sends
UDP
packet
client
UDP
clientSocket
socket
to network
UDP
socket
from network
2: Application Layer
22
Example: Java client (UDP)
import java.io.*;
import java.net.*;
Create
input stream
Create
client socket
Translate
hostname to IP
address using DNS
class UDPClient {
public static void main(String args[]) throws Exception
{
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName("hostname");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String sentence = inFromUser.readLine();
sendData = sentence.getBytes();
2: Application Layer
23
Example: Java client (UDP), cont.
Create datagram
with data-to-send,
length, IP addr, port
Send datagram
to server
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket);
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
Read datagram
from server
clientSocket.receive(receivePacket);
String modifiedSentence =
new String(receivePacket.getData());
System.out.println("FROM SERVER:" + modifiedSentence);
clientSocket.close();
}
}
2: Application Layer
24
Example: Java server (UDP)
import java.io.*;
import java.net.*;
Create
datagram socket
at port 9876
class UDPServer {
public static void main(String args[]) throws Exception
{
DatagramSocket serverSocket = new DatagramSocket(9876);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
while(true)
{
Create space for
received datagram
Receive
datagram
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
2: Application Layer
25
Example: Java server (UDP), cont
String sentence = new String(receivePacket.getData());
Get IP addr
port #, of
sender
InetAddress IPAddress = receivePacket.getAddress();
int port = receivePacket.getPort();
String capitalizedSentence = sentence.toUpperCase();
sendData = capitalizedSentence.getBytes();
Create datagram
to send to client
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress,
port);
Write out
datagram
to socket
serverSocket.send(sendPacket);
}
}
}
End of while loop,
loop back and wait for
another datagram
2: Application Layer
26
UDP observations & questions
Both client server use DatagramSocket
Dest IP and port are explicitly attached to
segment.
What would happen if change both clientSocket
and serverSocket to “mySocket”?
Can the client send a segment to server without
knowing the server’s IP address and/or port
number?
Can multiple clients use the server?
2: Application Layer
27
Appendix
Java Network Programming
Java I/O byte stream
Java I/O char stream
High level class in stream chaining
2: Application Layer
28
Java Network Programming
Java.io
InputStream, OutputStream byte
Reader, Writer text
Java.net
TCP Programming
• Java.net.Socket client, server
• Java.net.ServerSocket server
UDP Programming
• Java.net.DatagramSocket client, server
• Java.net.DatagramPacket create packet
2: Application Layer
29
Java I/O
byte streams
Java I/O
char streams
High Level Class
In Stream Chaining
Application Layer:
Socket Programming
Jaringan Komputer
Jurusan Ilmu Komputer/ Informatika
Universitas Diponegoro
2012/2013
Computer Networking:
A Top Down Approach,
5th edition.
Jim Kurose, Keith Ross
Addison-Wesley, April
2009.
2: Application Layer
1
Network Applications
1.
Protocol standard defined RFC
RFC 959 FTP
2. Proprietary
single developer client-server
Not to use one of the well-known port numbers
defined in the RFC.
T C P or UDP ?
T C P connection oriented, reliable
UDP connectionless, unreliable
2: Application Layer
2
Example of
Client Server Communication
2: Application Layer
3
Socket programming
Goal: learn how to build client/server application that
communicate using sockets
Socket API
introduced in BSD4.1 UNIX,
1981
explicitly created, used,
released by apps
client/server paradigm
two types of transport
service via socket API:
UDP
TCP
socket
An application-created,
OS-controlled interface
(a “door”) into which
application process can
both send and
receive messages to/from
another application
process
2: Application Layer
4
Socket programming basics
Server must be
running before
client can send
anything to it.
Server must have a
socket (door)
through which it
receives and sends
segments
Similarly client
needs a socket
Socket is locally
identified with a port
number
Analogous to the apt #
in a building
Client needs to know
server IP address and
socket port number.
2: Application Layer
5
Chapter 2: Application layer
2.1 Principles of
2.6 P2P applications
network applications
2.2 Web and HTTP
2.3 FTP (skip)
2.4 Electronic Mail
(skip)
2.7 Socket programming
with TCP
2.8 Socket programming
with UDP
SMTP, POP3, IMAP
2.5 DNS
2: Application Layer
6
Socket-programming using TCP
TCP service: reliable transfer of bytes from one
process to another
controlled by
application
developer
controlled by
operating
system
process
process
socket
TCP with
buffers,
variables
socket
TCP with
buffers,
variables
host or
server
internet
controlled by
application
developer
controlled by
operating
system
host or
server
2: Application Layer
7
Socket programming with TCP
Client must contact server
server process must first
be running
server must have created
socket (door) that
welcomes client’s contact
Client contacts server by:
creating client-local TCP
socket
specifying IP address, port
number of server process
When client creates
socket: client TCP
establishes connection to
server TCP
When contacted by client,
server TCP creates new
socket for server process to
communicate with client
allows server to talk with
multiple clients
source port numbers
used to distinguish
clients (more in Chap 3)
application viewpoint
TCP provides reliable, in-order
transfer of bytes (“pipe”)
between client and server
2: Application Layer
8
Client Socket, Welcoming Socket,
and Connection Socket
2: Application Layer
9
Client/server socket interaction: TCP
Server (running on hostid)
Client
create socket,
port=x, for
incoming request:
welcomeSocket =
ServerSocket()
TCP
wait for incoming
connection request connection
connectionSocket =
welcomeSocket.accept()
read request from
connectionSocket
write reply to
connectionSocket
close
connectionSocket
setup
create socket,
connect to hostid, port=x
clientSocket =
Socket()
send request using
clientSocket
read reply from
clientSocket
close
clientSocket
2: Application Layer
10
Stream jargon
Client
Process
process
output
stream
monitor
inFromUser
input
stream
outToServer
characters that flow into or
out of a process.
An input stream is attached to
some input source for the
process, e.g., keyboard or
socket.
An output stream is attached
to an output source, e.g.,
monitor or socket.
The DataOutputStream class
has some methods to convert
(and send out) data into any
primitif data type, depend on
our need; Such as byte,
integer, char, etc
keyboard
inFromServer
A stream is a sequence of
input
stream
client
TCP
clientSocket
socket
to network
TCP
socket
from network
2: Application Layer
11
Socket programming with TCP
Example client-server app:
1) client reads line from
standard input (inFromUser
stream) , sends to server via
socket (outToServer
stream)
2) server reads line from socket
3) server converts line to
uppercase,
4) Server sends back to client
4) client reads, prints modified
line from socket
(inFromServer stream)
2: Application Layer
12
Example: Java client (TCP)
import java.io.*;
import java.net.*;
class TCPClient {
public static void main(String argv[]) throws Exception
{
String sentence;
String modifiedSentence;
Create
input stream
Create
client socket,
connect to server
Create
output stream
attached to socket
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
Socket clientSocket = new Socket("hostname", 6789);
DataOutputStream outToServer =
new DataOutputStream(clientSocket.getOutputStream());
2: Application Layer
13
Example: Java client (TCP), cont.
Create
input stream
attached to socket
BufferedReader inFromServer =
new BufferedReader(new
InputStreamReader(clientSocket.getInputStream()));
sentence = inFromUser.readLine();
Send line
to server
outToServer.writeBytes(sentence + '\n');
modifiedSentence = inFromServer.readLine();
Read line
from server
System.out.println("FROM SERVER: " + modifiedSentence);
clientSocket.close();
}
}
2: Application Layer
14
Example: Java server (TCP)
import java.io.*;
import java.net.*;
class TCPServer {
Create
welcoming socket
at port 6789
Wait, on welcoming
socket for contact
by client
Create input
stream, attached
to socket
public static void main(String argv[]) throws Exception
{
String clientSentence;
String capitalizedSentence;
ServerSocket welcomeSocket = new ServerSocket(6789);
while(true) {
Socket connectionSocket = welcomeSocket.accept();
BufferedReader inFromClient =
new BufferedReader(new
InputStreamReader(connectionSocket.getInputStream()));
2: Application Layer
15
Example: Java server (TCP), cont
Create output
stream, attached
to socket
DataOutputStream outToClient =
new DataOutputStream(connectionSocket.getOutputStream());
Read in line
from socket
clientSentence = inFromClient.readLine();
capitalizedSentence = clientSentence.toUpperCase() + '\n';
Write out line
to socket
outToClient.writeBytes(capitalizedSentence);
}
}
}
End of while loop,
loop back and wait for
another client connection
2: Application Layer
16
TCP observations & questions
Server has two types of sockets:
ServerSocket and Socket
When client knocks on serverSocket’s “door,”
server creates connectionSocket and completes
TCP conx.
Dest IP and port are not explicitly attached to
segment.
Can multiple clients use the server?
2: Application Layer
17
Chapter 2: Application layer
2.1 Principles of
2.6 P2P applications
network applications
2.2 Web and HTTP
2.3 FTP (skip)
2.4 Electronic Mail
(skip)
2.7 Socket programming
with TCP
2.8 Socket programming
with UDP
SMTP, POP3, IMAP
2.5 DNS
2: Application Layer
18
Socket programming with UDP
UDP: no “connection” between
client and server
no handshaking
sender explicitly attaches
IP address and port of
destination to each segment
OS attaches IP address and
port of sending socket to
each segment
Server can extract IP
address, port of sender
from received segment
application viewpoint
UDP provides unreliable transfer
of groups of bytes (“datagrams”)
between client and server
Note: the official terminology
for a UDP packet is “datagram”.
In this class, we instead use “UDP
segment”.
2: Application Layer
19
Running example
Client:
User types line of text
Client program sends line to server
Server:
Server receives line of text
Capitalizes all the letters
Sends modified line to client
Client:
Receives line of text
Displays
2: Application Layer
20
Client/server socket interaction: UDP
Server (running on hostid)
create socket,
port= x.
serverSocket =
DatagramSocket()
read datagram from
serverSocket
write reply to
serverSocket
specifying
client address,
port number
Client
create socket,
clientSocket =
DatagramSocket()
Create datagram with server IP and
port=x; send datagram via
clientSocket
read datagram from
clientSocket
close
clientSocket
2: Application Layer
21
Example: Java client (UDP)
input
stream
Client
process
monitor
inFromUser
keyboard
Process
Input: receives
packet (recall
thatTCP received
“byte stream”)
UDP
packet
receivePacket
packet (recall
that TCP sent
“byte stream”)
sendPacket
Output: sends
UDP
packet
client
UDP
clientSocket
socket
to network
UDP
socket
from network
2: Application Layer
22
Example: Java client (UDP)
import java.io.*;
import java.net.*;
Create
input stream
Create
client socket
Translate
hostname to IP
address using DNS
class UDPClient {
public static void main(String args[]) throws Exception
{
BufferedReader inFromUser =
new BufferedReader(new InputStreamReader(System.in));
DatagramSocket clientSocket = new DatagramSocket();
InetAddress IPAddress = InetAddress.getByName("hostname");
byte[] sendData = new byte[1024];
byte[] receiveData = new byte[1024];
String sentence = inFromUser.readLine();
sendData = sentence.getBytes();
2: Application Layer
23
Example: Java client (UDP), cont.
Create datagram
with data-to-send,
length, IP addr, port
Send datagram
to server
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress, 9876);
clientSocket.send(sendPacket);
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
Read datagram
from server
clientSocket.receive(receivePacket);
String modifiedSentence =
new String(receivePacket.getData());
System.out.println("FROM SERVER:" + modifiedSentence);
clientSocket.close();
}
}
2: Application Layer
24
Example: Java server (UDP)
import java.io.*;
import java.net.*;
Create
datagram socket
at port 9876
class UDPServer {
public static void main(String args[]) throws Exception
{
DatagramSocket serverSocket = new DatagramSocket(9876);
byte[] receiveData = new byte[1024];
byte[] sendData = new byte[1024];
while(true)
{
Create space for
received datagram
Receive
datagram
DatagramPacket receivePacket =
new DatagramPacket(receiveData, receiveData.length);
serverSocket.receive(receivePacket);
2: Application Layer
25
Example: Java server (UDP), cont
String sentence = new String(receivePacket.getData());
Get IP addr
port #, of
sender
InetAddress IPAddress = receivePacket.getAddress();
int port = receivePacket.getPort();
String capitalizedSentence = sentence.toUpperCase();
sendData = capitalizedSentence.getBytes();
Create datagram
to send to client
DatagramPacket sendPacket =
new DatagramPacket(sendData, sendData.length, IPAddress,
port);
Write out
datagram
to socket
serverSocket.send(sendPacket);
}
}
}
End of while loop,
loop back and wait for
another datagram
2: Application Layer
26
UDP observations & questions
Both client server use DatagramSocket
Dest IP and port are explicitly attached to
segment.
What would happen if change both clientSocket
and serverSocket to “mySocket”?
Can the client send a segment to server without
knowing the server’s IP address and/or port
number?
Can multiple clients use the server?
2: Application Layer
27
Appendix
Java Network Programming
Java I/O byte stream
Java I/O char stream
High level class in stream chaining
2: Application Layer
28
Java Network Programming
Java.io
InputStream, OutputStream byte
Reader, Writer text
Java.net
TCP Programming
• Java.net.Socket client, server
• Java.net.ServerSocket server
UDP Programming
• Java.net.DatagramSocket client, server
• Java.net.DatagramPacket create packet
2: Application Layer
29
Java I/O
byte streams
Java I/O
char streams
High Level Class
In Stream Chaining