The READ command may be used to obtain data from a socket.A READ operation terminates if any of the following are detected, in the order specified below:
|
Terminating Condition |
Argument Contains |
$Device |
$Key (Continued) |
|
Error |
Empty string |
Error string |
Empty string |
|
Timeout |
Data received before timeout |
Empty string |
Empty string |
|
Delimiter |
Data up to, but not including the delimiter |
Empty string |
Delimiter string |
|
Fixed length met |
String of fixed length |
Empty string |
Empty string |
|
Buffer emptied |
One (1) to as many characters as happen to be provided by the transport interface |
Empty string |
Empty string |
A non-fixed-length read, with no timeout and no delimiters requires a complex implementation of sequence of READs to ensure a predictable result. This is because the transport layer stream fragments delivered to the reader has only accidental correspondence with the operations performed by the writer. For example, the following
Write "Message 1","Message 2"
is presented to the reader as the stream "Message1Message2" but it can take from one (1) to 18 READ commands to retrieve the entire stream.