owserver protocol
owserver network protocol
- Motivation
Paul Hilton started this discussion in the developer's list:
http://article.gmane.org/gmane.comp.file-systems.owfs.devel/1501
- What is it?
owserver separates the "front-end" applications using 1-wire (owfs owhttpd ...) from the actual adapter. In the process, it allows remote 1-wire adapters, and multiplexing (more than one front-end client ber adapter). The communication uses network messaging, specifically TCP over an arbitrary port.
- Broad structure
A client initiates an exchange with owserver. Except for directory listings, there is a single client message and server response per interaction.
- Message format:
This is defined in the source code at /module/owlib/src/include/ow_message.h
| to Server | Fixed header | version | assure protocol compatibility | 4-byte network order |
|---|---|---|---|---|
| payload | length (in bytes) of payload data | 4-byte network order | ||
| type | type of function call | 4-byte network order | ||
| control_flags | format flags | 4-byte network order | ||
| size | size of data element (for read or write) | 4-byte network order | ||
| offset | offset for read or write | 4-byte network order | ||
| Variable payload | variable length raw data | |||
| to Client | Fixed header | version | assure protocol compatibility | 4-byte network order |
| payload | length (in bytes) of payload data | 4-byte network order | ||
| ret | return value of function call | 4-byte network order | ||
| control_flags | format flags | 4-byte network order | ||
| size | size of data element (for read or write) | 4-byte network order | ||
| offset | offset for read or write | 4-byte network order | ||
| Variable payload | variable length raw data | |||
- Message details see module/owlib/src/c/ow_server.c and module/owserver/src/c/owserver.c
| Message types | explanation | direction | payload | size | ret value | Payload contents |
|---|---|---|---|---|---|---|
| read | Get a value | TO | name length | expected size | -- | filename |
| BACK | size | -- | 0 if ok | value | ||
| write | Set a value | TO | name+value length | value length | -- | filename+value |
| BACK | 0 | -- | 0 if ok | -- | ||
| dir | list a directory | TO | name length | -- | -- | dir name |
| BACK | name length | -- | 0 if ok | directory element | ||
| BACK | ... | |||||
| BACK | 0 | end of list marker | ||||
| size(obsolete) | length of a data field | TO | name length | -- | -- | filename |
| BACK | 0 | 0 | <0 error, >0 length | -- | ||
| presence | check existence of a device | TO | name length | -- | -- | filename |
| BACK | 0 | -- | 0 if ok | -- | ||
| ping | response after 1.5 sec while gathering data | TO | (none) | |||
| BACK | <0 | -- | -- | -- | ||
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