Sockets API

1
Sockets API

• Overview
• Sockets with UDP
• Sockets with TCP
• Fast Sockets (Fast UDP)
• IP Multicasting

2
Sockets Overview

• WHAT IT IS
• Used by applications to send and receive data
  over TCP/IP networks
• WHAT IT DOES
• Supports UDP and TCP protocols
• Sends and receives data between applications
• SET-UP CONDITIONS
• Socket() call creates communications endpoints
• Bind() links a network address to the socket
• Other calls depend on the protocol

3
Socket-Layer Protocols

• Application Level Network Communication Protocols
• Ride on Top of Either TCP/IP for Guaranteed
  Delivery or UDP/IP for Minimizing Network Traffic
  (not Guaranteed)
• Inconspicuous Communication for Security

INTERNET
Socket
Socket Connection
4
Possible Socket Implementations
TCP Connection
Server
Client
Socket Connection
Client creates socket, requests connection on
specific IP port. Server must have been passively
listening on that port.
5
Sockets Flow - UDP
Device 1
Device 2
Create
Create
Bind
Bind
SendTo
SendTo
NETWORK
RecvFrom
RecvFrom
6
Sockets Flow - TCP
Client
Server
Create
Create
(Associate Socket with own IP addr, port)
Bind
Bind
Connect
Listen
NETWORK
Accept
Send
Send
Recv
Recv
7
Example API call
include ltsockapi.hgt

• Declaration
• int connect(int socket_descriptor,
• struct sockaddr_in ptr2Inet_socket_addr_struct,
  int addrlen)
• Establish Connection
• / Setup the server's sockaddr_in struct /
• bzero(serverAddress, sizeof(serverAddress))
• serverAddress.sin_family AF_INET
• serverAddress.sin_port htons(13)
• serverAddress.sin_addr.s_addr
  htonl(0xC75CBA53) / 199.92.186.83 /
• int rc (connect(69, serverAddress,
  sizeof(serverAddress))
• Return value
• 0 if successful, otherwise -1.

8
Fast UDP (Fast Sockets)

• Socket-like API that bypasses most of the stack
• Advantages of Fast UDP API performance -
  potentially double the data rate
• Advantages of Normal Sockets API portable,
  richer API, TCP support
• Utilizes a different set of API calls

9
Fast UDP vs. Standard Socket APIs

• Standard
• accept
• bind
• connect
• closesocket
• connect
• getpeername
• gGetsockname
• getsockopt
• listen
• recv
• recvfrom
• send
• sendto
• setsocketopt
• shutdown
• socket

• Fast UDP
• fBind
• fGetBuf
• fSendTo
• fSockInit
• fSocket
• fSocketClose

10
IP Multicasting

• NETOS TCP/IP supports Level 2 IP multicast as
  defined by RFC 1112, which includes sending and
  receiving IP multicast packets and implementation
  of the Internet Group Membership Protocol (IGMP)
  V1.
• To enable a static interface to have multicast
  capability, the n_mcastlist field of the
  netstatic entry to point be set to a call back
  function, mcastlist. The function mcastlist is
  defined in the file narmenet.c (in the src\bsp
  directory).
• If n_mcastlist field of a static interface be set
  to NULL, that interface won't be able to
  send/receive multicast packets.
• The setsockopt() function is used to add/delete
  memberships and set multicast options for a
  particular socket.