ProSoft Technology MVI56E-LDM - Manual (Page 53)

ControlLogix Platform ♦ "C" Programmable Understanding the MVI56-LDM API
Linux Application Development Module Developer's Manual
ProSoft Technology, Inc. Page 47 of 264
March 12, 2014
 The call to the function
bind()
assigns the address specified in the structure
serv_addr
to the socket created by the call to
socket()
.
 The call to the function
listen()
with second arguments as '10' specifies the
maximum number of client connections that the server will queue for this
listening socket.
 The call to
listen()
makes this socket a functional listening socket.
 Code enters an infinite while loop in which:
o the call to accept() puts the server to sleep waiting for an incoming client
request. When a request is received, and the three-way TCP handshake
is complete,
accept() wakes up and returns the socket description
representing the client socket.
o time()
is called to read the current system time
o Snprintf
is used to pu the time into the send buffer in a human-readable
format
o write()
is then called to send formatted time to the client
o close()
is then used to close the connection to the client
o sleep()
is invoked to yield the processor for 1 second
Client ENetSample
To run the Client Enet sample:
1 Open a command window using telnet or a similar terminal software on the
PC through a serial (P1) or Ethernet port.
2 Login as user: root, password: password.
The Ethernet port E1 is used to communicate with the server device. The server
and client devices must both be connected on the same IPv4 subnet.
Set the IPv4 address and mask of the first Ethernet port using the
ifconfig
command.
To execute the sample:
From the default home directory
/psft
, type the command
./Client_Sample
ip.address.of.server to run the program. The IP address of the server node
must be provide so the server will know which node is executing the server
program. The client will send a connection request to the server, print the
response from the server to the console, and then exit.
While looking at the the sample source, you'll see that the following occurs:

register
sigquit_handler
for four signals
 check command line and print usage message if required
 open the backplane using
open_backplane()
 initialize the LEDs on the front panel
 create a socket with a call to the
socket()
function
 initialize the server address (
serv_addr
) structure:
 indicate that an IPv4 address is going to be used with
AF_INET
 set the destination port as the well known port
SERVER_PORT_NUMBER
 Convert the string version of the server IP address to binary with
inet_pton()
 After changing the front panel display to run, connect() is called to create the
TCP connection to the server