On Wed, Jul 20, 2011 at 11:15 AM, Jeremy Noring <kid...@gmail.com> wrote:
> I updated my RTP client to the most recent version (2011.7.18) and I'm
> having trouble with RTP over TCP. Occasionally Live555 will get in a state
> where it no longer receives any data from the server, even though the server
> is completely alive.
>
> I narrowed down the problem to RTPInterface.cpp, line 379:
>
> case AWAITING_STREAM_CHANNEL_ID: {
> // The byte that we read is the stream channel id.
> fStreamChannelId = c;
> fTCPReadingState = AWAITING_SIZE1;
> break;
> }
>
> ....fStreamChannelId gets set to some crazy value (e.g. '37') that isn't
> valid (for my app, should be 0 or 2). Once it's in that bad state, this
> fails repeatedly:
>
> case AWAITING_PACKET_DATA: {
> // Call the appropriate read handler to get the packet data from the
> TCP stream:
> RTPInterface* rtpInterface = lookupRTPInterface(fStreamChannelId);
> if (rtpInterface != NULL) {
>
> ...lookupRTPInterface(fStreamChannelId) returns NULL, which causes the
> library not to call fReadHandlerProc(). Live555 consumes all the CPU, and
> the only communication that still happens are the periodic SR reports (which
> do still work).
>
> I haven't managed to figure out why this is; using a debug build (i.e.
> DEBUG is defined, so there are periodic log messages) seems to reproduce the
> issue much more immediately--otherwise it can take a while to get in this
> bad state.
>
> Any ideas why this may be happening?
>
Update: I went through some older versions of the library (prior to the
async client rewrite) and I saw code that would ensure the stream channel ID
was present. So I did a quick test with the following code:
case AWAITING_STREAM_CHANNEL_ID: {
// The byte that we read is the stream channel id.
RTPInterface* rtpInterface = lookupRTPInterface(c);
if (rtpInterface != NULL)
{
fStreamChannelId = c;
fTCPReadingState = AWAITING_SIZE1;
}
else
{ // we're not interested in this channel
fTCPReadingState = AWAITING_DOLLAR;
}
...and that seems to have mostly corrected the issue. That said, I'd really
like to know how it's happening in the first place--seems to me like there
must be some other bug allowing it to get in this state? Or maybe it's not
that simple. Any insight is welcome.
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