Endpoint Interface

Using the Endpoint Interface

Specifying Flags for Receiving

23

For certain communication tools, it may be necessary to use special protocol flags
when receiving data. You do this by specifying one or more flag constants in the

rcvFlags

slot in the input spec. You can use such flags only if the communication

tool supports them.

For example, some of the built-in communication tools, such as the infrared and
AppleTalk tools, support only framed receiving (packetized data). In order to use
framed receiving, you must set the

rcvFlags

slot to the constant

kPacket

. With

the infrared tool, if you do not specify a

rcvFlags

value of

kPacket

, the tool

will behave unexpectedly.

Do not define the

rcvFlags

slot if the underlying communication tool does not

support EOP indicators. If you do so, your input will terminate after each physical
buffer of data is received. If you wish to terminate an input spec based on an EOP
indicator, set the

useEOP

slot in the

termination

frame to

true

.

Of the built-in communication tools, only the infrared, AppleTalk, and framed
asynchronous serial tools support framed packets and the

kPacket

flag.

If you set the

kPacket

flag and set the

useEOP

slot to

true

, you cannot also use

the

byteCount

slot in the termination frame--if you do,

byteCount

will be

ignored. In this case, only an EOP indicator will terminate input. If you do want to
use the

byteCount

slot with the

kPacket

flag, set the

useEOP

slot to

nil

. In

the latter case, the remote system should send an EOP indicator with every packet,
though input won't terminate until the

byteCount

condition is met.

Specifying an Input Time-Out

23

You can specify a time-out for input in the

reqTimeout

slot of the input spec. In

this slot, you specify the time, in milliseconds, of inactivity to allow during input.
If there is no input for the specified interval, the time-out expires, the input is
terminated, and the

CompletionScript

message is sent to the input spec frame.

In this case, the result code passed with the

CompletionScript

message

is ­16005.

Don't specify a

reqTimeout

value less than 30 milliseconds.

Note that if a time-out expires for an asynchronous request such as receiving, that
request and all outstanding requests are canceled.

Specifying Data Filter Options

23

As incoming data is received in the input buffer, the data can be processed, or
filtered. This filtering can occur on all types of received data, except binary data
(defined by the

'binary

data form). This filtering of data is defined by the

filter