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Once the connections has been established, the Client asks the Server to do something or to return some data by mean of a specific application protocol named TCP_DCS.
The Client sends always Command packets and the Server answers with Ok packets, Result packets or Error packets.
Both commands from a Client and answers from the Server always starts with a Header packet.
The Header packet will not be shown in the following description; think of it as always there. But logically, it "precedes the packet" rather than "is included in the packet" (See fig. 1).
| Code Block | ||||
|---|---|---|---|---|
| ||||
Bytes Name ----- ---- 4 packet Length 4 Transaction ID 4 Unit ID |
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Opcode | Name | Associated function and parameters |
0x00000000 | DO_NOT_USE | 0x00000000 must NOT be used |
0x00000001 | FETCH | fetch the STA or DYN fork: <elementName>,STA|DYN |
0x00000002 | SEND CMD 1 TO 3 | send a command from the console to the DEVIL: <command_string> |
0x00000003 | FETCH_BUFFER | fetch n bytes from a buffer global variable: <#OfBytes> |
0x00000004 | ECHO | send n bytes ang get the same n byte back: <byte_string> |
0x00000005 | FETCH_BLOCK | fetch STA or DYN fork (full array): <elementName>,STA|DYN (the elementName is used by the servlet just to recognize the proper class and can be any elementName belonging to that class in that DEVIL) |
0x00000006 | GET_ALIVE_COUNT | read the DEVIL alive counter: no arguments |
0x000000xx | to be defined | to be defined |
0x000000ff | DO_NOT_USE | 0x000000ff must NOT be used |
Fig. 1 - Structure of a command packet.
| Code Block | ||
|---|---|---|
| ||
Bytes Name ----- ---- 4 packet code, always = 0x00000000 |
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