Re: Talk to us first before you start reversing our protocol

[Frank Terbeck]

Hi!

niahoo osef wrote:
[...]
> With a friend, we are trying to implement the protocol of sending commands to
> xmms2 via TCP in Elixir (or Erlang). We feel it's hard to find the appropriate
> documentation but I eventually managed to gather some information on the wiki,
> hence the title of this email.

When I was implementing a client library  in Scheme¹, I was faced with a
similar problem.  I have been  making a couple  of notes² along  the way
that may be helpful.

> At the moment, we are able to send a hello command to the server. We figured
> how to do this by looking at the code of a javascript client.
>
> I would like to know where is the more fiable source that says that a "hello"
> command is "32", that an error type is "1", integer is "2" and must be 64bits,
> how to properly encode payload and what to expect in return, …

Most of  the server's API is  actually documented in a  machine readable
file³, which  you should use to  generate most of your  library. This is
true for constants (like what command id is correct for HELLO?) as well.

There are only a  couple of constants I couldn't find  in that spec, and
those are the identifiers for the protocol's types.

> I don't mind reading any code but I'm far from good at C. I can't find the
> python source code for a module named "xmmsapi" that xmmsclient depends on.

If Scheme makes you happier, feel free to  take a look at what I got⁴. I
think the first  ability you need is  to read data from  the server. For
that you  need to  be able to  parse a message's  header. Then  you need
serialisation and deserialisation  of the protocol's data  types to deal
with building and reading payload to and from the server. And after that
you can generate the actual API from ipc.xml.


Regards, Frank

¹ https://github.com/ft/xmms2-guile

² https://github.com/ft/xmms2-guile/blob/master/doc/xmms2-protocol.mdwn
  If you  clone the repository  and have pandoc installed,  this renders
  into  a PDF  as well  — I  don't know  if github's  Markdown rendering
  understands all the markup.

³ https://github.com/xmms2/xmms2-devel/blob/master/src/ipc.xml

⁴ https://github.com/ft/xmms2-guile/tree/master/tests

-- 
In protocol design, perfection has been reached not when there is
nothing left to add, but when there is nothing left to take away.
  -- RFC 1925

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Re: xmms2 last.fm scrobbler

[Frank Terbeck]

Hey Mehturt,

thanks for working on this! I tried it out and it seems to work fine
with MP3 files. However, when I put playback onto an ogg-vorbis file, I
get a slew of warnings and the file is not actually scrobbled at last.fm:

15:53:39  INFO in core: ../src/xmms/xform.c:1335: Successfully setup chain for 
'file:///home/hawk/audio/music/Fear+Factory/Obsolete/05+-+Descent.ogg' (4232) 
containing gvfs:magic:vorbis:segment
Use of uninitialized value in division (/) at 
/home/hawk/.config/xmms2/startup.d/scrobbler.pl line 188.
Use of uninitialized value $artist in concatenation (.) or string at 
/home/hawk/.config/xmms2/startup.d/scrobbler.pl line 191.
Use of uninitialized value $title in concatenation (.) or string at 
/home/hawk/.config/xmms2/startup.d/scrobbler.pl line 191.
Use of uninitialized value $album in concatenation (.) or string at 
/home/hawk/.config/xmms2/startup.d/scrobbler.pl line 191.
Use of uninitialized value $album in concatenation (.) or string at 
/home/hawk/.config/xmms2/startup.d/scrobbler.pl line 29.
Use of uninitialized value $artist in concatenation (.) or string at 
/home/hawk/.config/xmms2/startup.d/scrobbler.pl line 31.
Use of uninitialized value $track in concatenation (.) or string at 
/home/hawk/.config/xmms2/startup.d/scrobbler.pl line 34.
Use of uninitialized value $artist in concatenation (.) or string at 
/home/hawk/.config/xmms2/startup.d/scrobbler.pl line 53.
Use of uninitialized value $track in concatenation (.) or string at 
/home/hawk/.config/xmms2/startup.d/scrobbler.pl line 53.
Use of uninitialized value $title in string ne at 
/home/hawk/.config/xmms2/startup.d/scrobbler.pl line 205.


Note, that line numbers might be off by one or two, since I am using a
"use lib ..." line on top of the scrobbler.pl file, so that I don't have
to install the module, but can just use the whole thing from its git
repository.


Regards, Frank

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[PATCH 1/2] Set `CURLOPT_NOSIGNAL' to 1 to avoid crashes with multithreaded DNS

[Frank Terbeck]

This fixes http://bugs.xmms2.org/view.php?id=2546

Erik Massop noted:

  In unix systems, CURLOPT_NOSIGNAL need to be used if you're using the
  default resolver, as it will use signals to time-out otherwise and
  signals and threads don't mix.

  But ideally, you switch to using the c-ares resolver then to get
  proper timeouts even without signals.

...which he quoted from:

  
http://sourceforge.net/tracker/index.php?func=detailaid=2781096group_id=976atid=100976

Signed-off-by: Frank Terbeck f...@bewatermyfriend.org
---
 src/xmms2-scrobbler.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/xmms2-scrobbler.c b/src/xmms2-scrobbler.c
index 244fccb..a19eca2 100644
--- a/src/xmms2-scrobbler.c
+++ b/src/xmms2-scrobbler.c
@@ -317,6 +317,7 @@ do_handshake (Server *server)
 
set_proxy (server, curl);
 
+   curl_easy_setopt (curl, CURLOPT_NOSIGNAL, 1);
curl_easy_setopt (curl, CURLOPT_URL, post_data);
curl_easy_setopt (curl, CURLOPT_WRITEFUNCTION,
  handle_handshake_reponse);
@@ -400,6 +401,7 @@ curl_thread (void *arg)
 
set_proxy (server, curl);
 
+   curl_easy_setopt (curl, CURLOPT_NOSIGNAL, 1);
curl_easy_setopt (curl, CURLOPT_POST, 1);
curl_easy_setopt (curl, CURLOPT_WRITEFUNCTION,
  handle_submission_reponse);
-- 
1.8.2.rc1


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[PATCH 2/2] Include stdio.h and add two helper macros

[Frank Terbeck]

Since 22d52344e1745068e2bc7dd716bf9ec5dc7b8a06 in xmms2, you need to
include stdlib.h and stdio.h yourself.

Also, the macros XPOINTER_TO_INT() and XINT_TO_POINTER() are now in a
private header rather than the public one that gets installed to the
system. That makes it a little hard to use said macros. To solve the
issue, I'm just defining the macros as they are in the private header.

Signed-off-by: Frank Terbeck f...@bewatermyfriend.org
---
 src/submission.c  | 1 +
 src/xmms2-scrobbler.c | 8 
 2 files changed, 9 insertions(+)

diff --git a/src/submission.c b/src/submission.c
index 422db0a..326b003 100644
--- a/src/submission.c
+++ b/src/submission.c
@@ -22,6 +22,7 @@
  */
 
 #include stdlib.h
+#include stdio.h
 #include submission.h
 
 Submission *
diff --git a/src/xmms2-scrobbler.c b/src/xmms2-scrobbler.c
index a19eca2..ec3f1e4 100644
--- a/src/xmms2-scrobbler.c
+++ b/src/xmms2-scrobbler.c
@@ -48,6 +48,14 @@
 
 #define INVALID_MEDIA_ID -1
 
+#if defined(__x86_64__)
+#  define XPOINTER_TO_INT(p)  ((int)  (long)  (p))
+#  define XINT_TO_POINTER(i)  ((void *)  (long)  (i))
+#else
+#  define XPOINTER_TO_INT(p)  ((int)  (p))
+#  define XINT_TO_POINTER(i)  ((void *)  (i))
+#endif
+
 typedef struct {
char name[NAME_MAX + 1];
int hard_failure_count;
-- 
1.8.2.rc1


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