- Application Programming Interface:
- Application Programming Interface (API) = is a collection of library functions through which application programmers (= you can gain access to the services (provided by the system)
- Network APIs:
- The network communication services
are accessed
through 2 commonly used network APIs:
- Berkeley Sockets API
- (ATT's) Transport Layer Interface (TLI) --- has been superseded by XTI
- The network communication services
are accessed
through 2 commonly used network APIs:
- Today:
- Berkeley sockets is now by far the most popular Network API
(We will learn Berkeley sockets....)
- Communication endpoint:
- Communication endpoint = a logical location where messages are transmitted/received
- 2 kinds of
communication endpoints
- User program endpoint =
an object used in an
user program that
represents a
communication endpoint
- (Operating) System endpoint = an object used in the Operating System that represents a communication endpoint
- User program endpoint =
an object used in an
user program that
represents a
communication endpoint
- Ports:
- Port =
a communication end-point inside
the Operating System
- Ports can make use of the network interface card of the computer to transmit messages
Graphically:
- Port =
a communication end-point inside
the Operating System
- Types of ports:
- The Operating System
commonly implements
2 different types of
ports that provide
different type of
communication services
- User Datagram Protocol (UDP)
ports:
- UDP ports provides unreliable communication service
- Transport Control Protocol (TCP) ports:
- TCP ports provides reliable communication service
- The Operating System
commonly implements
2 different types of
ports that provide
different type of
communication services
- Socket:
- Socket =
a communication endpoint in
a network program
- The network application program can send and receive messages through sockets
- A socket must be associated (bound) to some port inside the Operating System !!!
- Socket =
a communication endpoint in
a network program
- Network programming model in
computer programs
Explanation:
- A socket can be
bound to
some port in the
Operating System
- The computer program will use the socket to transmit message through the port to which the socket was bound
- A socket can be
bound to
some port in the
Operating System
- Different types of sockets:
- There are different types
of sockets
- Each type of socket provides a specific quality of service
- There are different types
of sockets
- There are two types
of sockets in use today
- UDP sockets
- A UDP socket is
bound to an
UDP port
- UDP sockets will
therefore provides
unreliable communication
service
- The UDP socket uses a packet-oriented protocol: a unit of transmission is a packet
- A UDP socket is
bound to an
UDP port
- TCP sockets
- A TCP socket is
bound to an
TCP port
- TCP sockets will therefore
provides
reliable communication service
- TCP socket uses a byte-oritented protocol: the unit of transmission is a byte
- A TCP socket is
bound to an
TCP port
- UDP sockets