CORDET Framework - C2 Implementation
CrDemoSlave2/CrDaClientSocket.h File Reference

Interface for the client socket used in the CORDET Demo. More...

Go to the source code of this file.

Functions

void CrDaClientSocketInitAction (FwPrDesc_t prDesc)
 Initialization action for the client socket. More...
 
void CrDaClientSocketShutdownAction (FwSmDesc_t smDesc)
 Shutdown action for the client socket. More...
 
void CrDaClientSocketInitCheck (FwPrDesc_t prDesc)
 Initialization check for the client socket. More...
 
void CrDaClientSocketConfigAction (FwPrDesc_t prDesc)
 Configuration action for the client socket. More...
 
void CrDaClientSocketPoll ()
 Poll the client socket to check whether a new packet has arrived. More...
 
CrFwPckt_t CrDaClientSocketPcktCollect (CrFwDestSrc_t pcktSrc)
 Function implementing the Packet Collect Operation for the client socket. More...
 
CrFwBool_t CrDaClientSocketIsPcktAvail (CrFwDestSrc_t pcktSrc)
 Function implementing the Packet Available Check Operation for the client socket. More...
 
CrFwBool_t CrDaClientSocketPcktHandover (CrFwPckt_t pckt)
 Function implementing the hand-over operation for the client socket. More...
 
void CrDaClientSocketSetPort (int n)
 Set the port number for the socket. More...
 
void CrDaClientSocketSetHost (char *name)
 Set the host name of the server. More...
 

Detailed Description

Interface for the client socket used in the CORDET Demo.

The CORDET Demo consists of three applications which communicate with each other via sockets. This module defines the functions through which the InStreams and OutStreams of the Master and Slave Applications control a client socket in order to receive packets (InStream) or to send them (OutStream). These functions are used to customize the InStreams which interact with the socket. More precisely:

The functions in this module should be accessed in mutual exclusion. Compliance with this constraint is not enforced and is therefore under the responsibility of the caller.

The socket controlled by this module is built as a client socket using the Internet domain and the TCP protocol. It is designed to work with the server socket of CrDaServerSocket.h.

The socket must be initialized with the port number and with the host name for its socket (these are defined through functions CrDaClientSocketSetPort and CrDaClientSocketSetHost).

The socket assumes a polling approach for incoming packets: function CrDaClientSocketPoll should be called periodically by an external scheduler. This function performs a non-blocking read on the socket to check whether a packet is available at the socket. If a packet is available, the function retrieves its source and forwards it to the associated InStream by calling function CrFwInStreamPcktAvail on the InStream to signal the arrival of a new packet. This causes all pending packets from that source to be collected by the InStream and stored in its Packet Queue.

The implementation of this module assumes that, at each read operation, an entire packet is received. The situation where the packet is split into fragments during the transmission process is not handled. In practice, this socket is intended for the case where the socket is local to the host platform (i.e. where the host name is "localhost" and both sender and receiver of a packet are located on the same platform).

Packets which are read from the socket are stored in a buffer (the Read Buffer). This is an array of bytes whose size is equal to the maximum size of a middleware packet. The Read Buffer can be either "full" (if its first byte is different from zero) or "empty" (if its first byte has been cleared).

The packet hand-over operation for OutStreams is implemented in function CrDaClientSocketPcktHandover which performs a non-blocking write to the socket.

If an error is encountered while performing a system call, this module uses function perror to print an error message and, if the error was encountered in the initialization or configuration action, it sets the outcome of the action to 0 ("failure") and returns.

This module assumes that the maximum length of a packet is smaller than 256 bytes. Compliance with this constraint is verified in the Initialization Check.

Mode of Use of a Client Socket Module

This module may be controlled jointly by multiple InStreams and/or OutStreams. Its socket is initialized when the first of these components is initialized (the initialization of the other InStreams/OutStreams has no effect). The socket is reset whenever one of the InStreams/OutStreams is reset. The socket is shut down whenever one of the InStreams/OutStreams is shut down (the shutdown of the other InStreams/OutStreams has no effect).

This client socket should only be initialized after its server socket has completed its initialization.

After the client socket has completed its configuration, users should periodically call function CrDaClientSocketPoll to poll the socket for any incoming packets.

If the server socket is closed, a call to the socket read operation in the client socket (i.e. a call to CrDaClientSocketPoll) will result in the last packet sent by the server socket being read from the socket. Hence, correct operation requires that the client socket be shutdown before server socket.

Author
Vaclav Cechticky vacla.nosp@m.v.ce.nosp@m.chtic.nosp@m.ky@p.nosp@m.np-so.nosp@m.ftwa.nosp@m.re.co.nosp@m.m
Alessandro Pasetti paset.nosp@m.ti@p.nosp@m.np-so.nosp@m.ftwa.nosp@m.re.co.nosp@m.m

This file is part of the CORDET Framework.

This Source Code Form is subject to the terms of the Mozilla Public License, v. 2.0. If a copy of the MPL was not distributed with this file, You can obtain one at http://mozilla.org/MPL/2.0/.

For information on alternative licensing, please contact P&P Software GmbH.

Definition in file CrDemoSlave2/CrDaClientSocket.h.

Function Documentation

void CrDaClientSocketConfigAction ( FwPrDesc_t  prDesc)

Configuration action for the client socket.

This action clears the Read Buffer and executes the Configuration Action of the base InStream (function CrFwInStreamDefConfigAction)

Parameters
prDescthe configuration procedure descriptor.

Definition at line 173 of file CrDemoMaster/CrDaClientSocket.c.

void CrDaClientSocketInitAction ( FwPrDesc_t  prDesc)

Initialization action for the client socket.

If the client socket has already been initialized, this function calls the Initialization Action of the base InStream/OutStream and then returns. If the client socket has not yet been initialized, this action:

  • creates the Read Buffer;
  • creates and connects the socket as a non-blocking socket;
  • executes the Initialization Action of the base InStream/OutStream;
  • sets the outcome to "success" if the previous operations are successful.
Parameters
prDescthe initialization procedure descriptor.

Definition at line 67 of file CrDemoMaster/CrDaClientSocket.c.

void CrDaClientSocketInitCheck ( FwPrDesc_t  prDesc)

Initialization check for the client socket.

The check is successful if: the maximum length of a packet (as retrieved from CrFwPcktGetMaxLength) is smaller than 256; and the port number and server host name have been set.

Parameters
prDescthe initialization procedure descriptor.

Definition at line 150 of file CrDemoMaster/CrDaClientSocket.c.

CrFwBool_t CrDaClientSocketIsPcktAvail ( CrFwDestSrc_t  pcktSrc)

Function implementing the Packet Available Check Operation for the client socket.

This function implements the following logic:

  • The function begins by checking the Read Buffer.
  • If it is full and the source attribute of the packet it contains is equal to packetSource, the function returns 1.
  • If the Read Buffer is not full or it is full but the source attribute of the packet it contains is not equal to packetSource, the function performs a non-blocking read on the socket.
  • If the read operation returns nothing or returns a packet with a source attribute other than packetSource, the function returns 0.
  • If the read operation returns a packet with a source attribute equal to packetSource, the function stores it in the Read Buffer and then returns 1.
Parameters
pcktSrcthe source associated to the InStream
Returns
the value of a predefined flag

Definition at line 241 of file CrDemoMaster/CrDaClientSocket.c.

CrFwPckt_t CrDaClientSocketPcktCollect ( CrFwDestSrc_t  pcktSrc)

Function implementing the Packet Collect Operation for the client socket.

If the packet in the Read Buffer has a source attribute equal to packetSource, this function:

  • creates a packet instance through a call to CrFwPcktMake
  • copies the content of the Read Buffer into the newly created packet instance
  • clears the Read Buffer
  • returns the packet instance

If the Read Buffer holds a packet from a source other then packetSource, this function returns NULL. Note that the logic of the client socket module guarantees that the Read Buffer will always be full when this function is called.

Parameters
pcktSrcthe source associated to the InStream
Returns
the packet

Definition at line 223 of file CrDemoMaster/CrDaClientSocket.c.

CrFwBool_t CrDaClientSocketPcktHandover ( CrFwPckt_t  pckt)

Function implementing the hand-over operation for the client socket.

This function performs a non-blocking write on the socket and, if it succeeds, it returns 1; otherwise, it returns 0.

Parameters
pcktthe packet to be written to the socket
Returns
1 if the packet was successfully written to the socket; 0 otherwise.

Definition at line 275 of file CrDemoMaster/CrDaClientSocket.c.

void CrDaClientSocketPoll ( )

Poll the client socket to check whether a new packet has arrived.

This function should be called periodically by an external scheduler. It performs a non-blocking read on the socket to check whether a packet is available at the socket. If a packet is available, it is placed into the Read Buffer, its source is determined, and then function CrFwInStreamPcktAvail is called on the InStream associated to that packet source.

Definition at line 190 of file CrDemoMaster/CrDaClientSocket.c.

void CrDaClientSocketSetHost ( char *  name)

Set the host name of the server.

If a local socket is being created, the host name should be set to "localhost".

Parameters
namethe host number.

Definition at line 298 of file CrDemoMaster/CrDaClientSocket.c.

void CrDaClientSocketSetPort ( int  n)

Set the port number for the socket.

The port number must be an integer greater than 2000.

Parameters
nthe port number.

Definition at line 293 of file CrDemoMaster/CrDaClientSocket.c.

void CrDaClientSocketShutdownAction ( FwSmDesc_t  smDesc)

Shutdown action for the client socket.

If the client socket has already been shut down, this function calls the Shutdown Action of the base InStream/OutStream and then returns. If the client socket has not yet been shut down, this action executes the Shutdown Action of the base InStream/OutStream, releases the Read Buffer, and closes the socket.

Parameters
smDescthe InStream or OutStream State Machine descriptor.

Definition at line 134 of file CrDemoMaster/CrDaClientSocket.c.

P&P Software GmbH, Copyright 2012-2013, All Rights Reserved