DCN 3013: Network Programming

1
DCN 3013 Network Programming

• Muhammed Ramiza Ramli
• KUKTEM

2
Overview of UDP

• User Datagram Protocol (UDP) provides fewer
  services and requires more control by the
  programmer
• UDP is a connectionless protocol without
  guaranteed message delivery

3
UDP versus TCP

• UDP handles fewer detail than TCP
• does not ensure that messages are delivered (no
  report)?
• not ensure the order in which packets will be
  transferred (IP will split the packet)?

4
Advantages of TCP

• There are several advantages of TCP
• provides explicit connection creation and
  termination
• ensure reliable, ordered and unduplicated
  delivery of data
• handles flow control
• allow prioritization of data
• return an error condition if data is not
  delivered
• handles large data block by maintaining the
  connection and breaking the blocks into smaller
  pieces

5
Disadvantages of TCP

• Disagvantages
• a connection must be created and maintained while
  data is moving. making it slower - overhead

6
Advantages of UDP

• Advantages
• does not require a connection
• does not have the overhead of receiver
  acknowledging receipt of packets
• designed for a short application and control
  messages
• packet by packet basis requires less network
  bandwidth than TCP

7
Disadvantages of UDP

• Disadvantages
• programmer must create code to detect
  transmission error and retransmit (if required by
  application)?
• programmer must break down the larger packet

8
Why UDP?

• Look at how an application works.
• An application that sends out periodic message
  that are low importance or repeated
• An application that regularly broadcast status
  (periodic status)?
• based on importance of the data, volume of the
  data, and what level of transmission integrity.

9
TCP

• Client
• Create socket
• socket()?
• Initiate a connection
• connect()?
• Communicate
• send()/recieve()?

• Server
• Create socket
• socket()?
• Assign a name to the socket
• bind()?
• Establish a queue
• listen()?
• Extract connection from a queu
• accept()?
• Communicate
• send()/recieve()?

10
UDP

• Server
• Create a socket
• socket()?
• Assign a name to the socket
• bind
• receive data from client
• recvfrom
• send data to client
• sendto

• Client
• Create a socket
• socket()?
• Assign a name to the socket
• bind
• send data to server
• snedto()?
• receive data from server
• recvfrom()?

11
Sending Data with UDP

• There is no handshaking or confirmation that the
  other system is listening, receiving, or ever
  processing the data
• include ltsys/types.hgt
• include ltsys/socket.hgt
• int sendto( int s, const void msg, size_t len,
  int flags, const struct sockaddr to, socklen_t
  tolen)

12
Program

• int port 6789
• int socket_df
• char buf80
• struct sockaddr_in address
• address.sin_family AF_INET
• address.sin_addr.s_addr inet_addr(127.0.0.1)
• address.sin_port htons(port)
• convert the integer passed from host byte order
  to network byte order.
• socket_df socket(AF_INET, SOCK_DGRAM, 0)
• sendto(socket_df, buf, sizeof(buf), 0, (struct
  sockaddr) address, sizeof(address))
• close(socket_df)

13
receiving UDP Data

• UDP listen to a port for messages tranmitted from
  another system
• include ltsys/types.hgt
• include ltsys/socket.hgt
• int recvfrom(int s, void buf, size_t len, int
  flags, struct socketaddr from, socklen_t
  fromlen)

14
program

• int port 6789
• int sin_len
• char msg80
• int sock_df
• struct sockaddr_in sin
• sin.sin_family AF_INET
• sin.sin_addr.s_addr htonl(INADDR_ANY)
• sin.sin_port htons(port)
• sin_len sizeof(sin)
• sock_df socket(AF_INET,SOCK_DGRAM, 0)
• bind(sock_df, (struct sockaddr )sin,
  sizeof(sin))
• recvfrom(sock_df, msg, sizeof(msg), 0, (struct
  sockaddr) sin, sin_len)
• close(sock_df)