radare2/doc/rap

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RAP protocol
============
RAP stands for the Remote Access Protocol of Radare2, it is compatible with radare1
and it simply defines a communication between a client and a server to simulate IO
operations.
There are two different implementations, one in C and another in Python.
Usage example
-------------
Start in one terminal the following command to wait for incoming connections:
r2 rap://:9999
In another machine or terminal connect it:
r2 rap://localhost:9999//bin/ls
As you see, the path of the remote file to load must be specified, and this handled
by the open() packet.
Known Bugs
----------
* Read/Write operations ignore the filedescriptor completely because it is suposed to be handled by the IO layer and it is redundant, but it introduces a bug that breaks support for multiple files.
* This can be fixed with a new packet type RAP_SETFD.
* Read lengths should be only 2 bytes, there's no sense in read > 64K of memory in a shot.
* Seek does not returns anything
* System vs Cmd - the first should have a return value as well as string result
* Filedescriptors are asumed to be 32bit
Operations
----------
The protocol is designed to be bidirectional, but right now, only one way is supported.
The client sends a byte specifying the operation and the server will reply the same byte
masked with the RMT_REPLY value (0x80 | op)
RAP_OPEN = 1
RAP_READ = 2
RAP_WRITE = 3
RAP_SEEK = 4
RAP_CLOSE = 5
RAP_SYSTEM = 6
RAP_CMD = 7
RAP_REPLY = 0x80
This is how are constructed the packets:
RAP_OPEN
struct packed RapOpen {
ut8 op = 1;
ut8 rw = 0; // 0 = read-only, 1 = read-write
ut8 len = 15; // length of filename
}
>> 01 RW LN [....]
<< 81 FD=(.. .. .. ..)
RAP_READ
>> 02 LN=(.. .. .. ..)
<< 82 LN=(.. .. .. ..) [..LN..]
RAP_WRITE
>> 03 LN=(.. .. .. ..) [..LN..]
<< 83 LN=(.. .. .. ..)
RAP_SEEK
>> 04 FLAG=(..) OFFSET=(.. 8 bytes ..)
<< 84
RAP_CLOSE
>> 05 FD=(4 bytes)
<< 85 RET=(4 bytes)
RAP_SYSTEM
>> 06 LEN=(4 bytes) STR[LEN bytes]
<< 86 LN=(.. .. .. ..) STR[ LEN bytes]
RAP_CMD_
>> 07 LEN=(4 bytes) STR[LEN bytes]
<< 87 LN=(.. .. .. ..) STR[ LEN bytes]
Examples
--------
Python:
See radare2-bindings/python/remote.py and test-rap-*.py
C:
Server: libr/socket/rap_server.c
Client: libr/io/p/io_rap.c