Transcript Sockets - Digi International

Sockets API
Overview
Sockets with UDP
Sockets with TCP
Fast Sockets (Fast UDP)
IP Multicasting
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
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 Connection
Socket
Possible Socket
Implementations
TCP Connection
Client
Server
Socket Connection
Client creates socket, requests connection on specific IP port.
Server must have been passively ‘listening’ on that port.
Terminal
UDP Connection
Terminal
Socket Connection
Socket created on specific port, data is sent without connection established.
Remote terminal must have been passively ‘listening’ on that port.
Sockets Flow - UDP
Device 1
Device 2
Create
Create
Bind
Bind
DATA PIPE
SendTo
SendTo
NETWORK
RecvFrom
RecvFrom
Sockets Flow - TCP
Create
Bind
Client
Server
(Associate Socket
with own IP addr,
port)
Create
Bind
Listen
Connect
Accept
NETWORK
Send
Send
Recv
Recv
DATA PIPE
Example API call
Declaration
#include <sockapi.h>
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.
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
Fast UDP vs. Standard Socket
API’s
• Standard
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accept
bind
connect
closesocket
connect
getpeername
gGetsockname
getsockopt
listen
recv
recvfrom
send
sendto
setsocketopt
shutdown
socket
• Fast UDP
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fBind
fGetBuf
fSendTo
fSockInit
fSocket
fSocketClose
IP Multicasting
• NET+OS 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.