This section describes what is a datagram - An independent and self-contained message sent over the network whose arrival, arrival time, and content are not guaranteed.
Datagram: An independent and self-contained message sent over the network
whose arrival, arrival time, and content are not guaranteed. This definition
is copied from the Sun's Java tutorial document. A datagram should at least contain the
following information:
Address: The Internet address of the remote system.
Port: The port number of the remote system.
Data: The data contained in the datagram.
Datagram Socket: A logical concept represents the contact point on
the local system of a datagram communication link.
Internet Address: A unique number to identify each computer system on
the Internet.
Port: A number representing an entry point of on a computer system on
the Internet, where a two-way communication link can be established.
Local System: The computer system at this end of a communication
link.
Remote System: The computer system at the other end of a two-way
communication link.
A datagram communication link on the Internet involves:
Two computer systems, each has its own Internet address.
A port number on each computer system that is used only by this
communication link during the transmission period.
A program on each computer system that uses this communication link.
One program must act as the receiver of the datagram, and the other
program must act as the sender.
The receiver must create a datagram socket to represent the receiving
point of the communication link.
The sender must create a datagram socket to represent the sending
point of the communication link.
The following diagram illustrates how application programs can use
datagram socket send data to another computer system
through a datagram communication link on the Internet:
Computer System I Computer System II
Datagram|Address a| Internet |Address b|Datagram
Sender<--->Socket|Port 1 |----------->| Port 2|Socket<--->Receiver
