4.1 Specification of Connection Requirements

The pattern protocolSpec is used to package a specification of requirements to a communication transfer. This package is given to a portablePortAddress, which will then use it to choose an appropriate channel. A specification is built with an instance of protocolSpec by setting its cType and rType attributes. For these, choose from the constant values given in the fragment commError.

The cType value can be any of the constants commProtocol_... and specifies that the chosen channel must be a TCP/UDP/etc. connection or that any kind of connection will do (commProtocol_dontcare).

The value of rType is any of the constants commRely_dontcare (no requirements), commRely_unreliable (allow all the below mentioned kinds of malfunction) or commRely_reliable (prevent all those malfunctions). Or it is a sum of some of the constants commRely_loss (prevent packet lossage), commRely_dup (prevent packet duplication), commRely_order (prevent packets from arriving out of order), commRely_contents (prevent packets from having corrupt data).

In reality, the last guarantee is enforced by means of checksums or something similar, so it is only very unlikely that a packet with corrupt data will pass unnoticed, not impossible. Moreover, all the other guarantees depend on having packets with trustworthy (header) contents, so not all combinations make sense.

Process Libraries - Reference Manual
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[Modified: Friday October 20th 2000 at 14:22]