Prosoft-technology MVI56E-LDM Bedienungsanleitung PDF herunterladen (Seite 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

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