AMX DESIGN XPRESS V 1.5 - PROGRAMMER GUIDE User's Guide download pdf (Page 156)

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DAK

KwikNet Low Level Services

Starting and Stopping KwikNet

Most applications start KwikNet with a call to kn_enter() and allow KwikNet to run

forever. Some use kn_exit() to stop KwikNet in preparation for a termination of the

entire application. Others find it necessary to stop and then restart

KwikNet to recover

from serious network faults. The ability to start and stop

KwikNet on demand is also

useful when testing your network application.

KwikNet is started with a call to kn_enter(). Procedure kn_state() can then be used to

detect when KwikNet is fully operational.

KwikNet can only be stopped if you enabled KwikNet to shut down. This feature is enabled

by a configuration parameter in the KwikNet Network Parameter File used in the

construction of the

KwikNet Library as described in Chapter 2.3. When you define your

KwikNet configuration, simply check the option box labeled "KwikNet can be shut down" on

the General property page.

Before KwikNet can be stopped, your application must cease using all KwikNet services.

You must ensure that all KwikNet resources such as UDP channels and TCP or UDP

sockets have been relinquished. Do not forget that all dedicated KwikNet clients and

servers (such as those for FTP, HTTP, TELNET, TFTP, SMTP and SNMP) must have

been stopped in an orderly fashion. The private KwikNet DHCP and DNS clients will be

stopped by KwikNet.

KwikNet is stopped in two steps. The first step is to wait long enough for all unfinished

network transactions to complete. KwikNet procedure kn_godown() provides this service.

Your application can call kn_godown() to start the shutdown process and wait, up to

some maximum interval, for the process to complete.

The second step is to force KwikNet to shut down all networks and their device drivers and

release all memory and operating system resources. This process is initiated with a call

to kn_exit(). Procedure kn_exit() does not return to the caller until KwikNet has fully

stopped. Then, and only then, can KwikNet be restarted.

If your application does not call

kn_godown() to shut down KwikNet before calling

kn_exit(), KwikNet will automatically attempt a shutdown, waiting up to two minutes for

the process to complete before finally stopping. In this case, if the shutdown fails,

KwikNet will initiate a fatal exit.

In a multitasking system, procedures kn_godown() and kn_exit() can only be called

from an application task executing at lower priority than the KwikNet Task. In a single

threaded system, the procedures must be called from your App-Task.

Warning!

You must not shut down KwikNet unless KwikNet's memory

is allocated from a static array or from a fixed region of

memory acquired when KwikNet is started and released

when KwikNet is stopped.

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