Several STREAMS messages differ in their purpose and queueing priority. The message types are briefly described and classified, according to their queueing priority, in Table 7–1 and Table 7–2. A detailed discussion of message types is in Chapter 8, STREAMS Kernel-Level Mechanisms.
Some message types are defined as high-priority types. Ordinary or normal messages can have a normal priority of 0, or a priority (also called a band) from 1 to 255.
Table 7–1 Ordinary Messages, Description of Communication FlowTable 7–2 High-Priority Messages, Description of Communication Flow
Direction |
||
---|---|---|
M_COPYIN |
Upstream |
|
M_COPYOUT |
Upstream |
|
M_ERROR |
Upstream |
|
M_FLUSH |
Bidirectional |
|
M_HANGUP |
Upstream |
|
M_UNHANGUP |
Upstream |
|
M_IOCACK |
Upstream |
|
M_IOCDATA |
Downstream |
|
M_IOCNAK |
Upstream |
|
M_PCPROTO |
Bidirectional |
|
M_PCSIG |
Upstream |
|
M_READ |
Downstream |
|
M_START |
Downstream |
|
M_STARTI |
Downstream |
|
M_STOP |
Downstream |
|
M_STOPI |
Downstream |