UDP send data loss

[dogmaphobic]

This is related to #1696.

Is there a way to expose this to WiFiUdp.h?

https://github.com/esp8266/Arduino/blob/master/libraries/Ethernet/src/utility/socket.cpp#L409

That is, a way to check the status of the buffer before attempting to write?

From WiFiUdp, we don't have access to the underlying socket. If the socket was exposed, I could do something like:

WiFiUDP   udp;

<...>
udp setup and configured, etc.
<...>

uint16_t bufferFreeSize()
{
  uint16_t ret =0;
  SPI.beginTransaction(SPI_ETHERNET_SETTINGS);
    ret = W5100.getTXFreeSize(udp.socket());
  }
  SPI.endTransaction();
  return ret;
}

Thanks!

Want to back this issue? Post a bounty on it! We accept bounties via Bountysource.

[igrr]

As mentioned in #1696 (comment), the issue here is that underlying netif implementation doesn't return an error code when UDP packet gets lost. Also there is no API in Espressif SDK which would allow one to query the amount of space left in TX buffer chain. I'll see is we can add one though.

[dogmaphobic]

Also there is no API in Espressif SDK which would allow one to query the amount of space left in TX buffer chain

What about W5100.getTXFreeSize(udp.socket())?

I (think) I understand the restrictions of the Espressif SDK. Yes, getting access to the state of the actual socket buffer would be great but in the mean time, what about the above? When I call write() (in between a beginPacket() and endPacket()) I often get a return value, which is less than the amount of data I had requested to send. That's a result of a query to W5100.getTXFreeSize(udp.socket()) at a lower level. Knowing that free buffer size ahead of time would already help a lot. I can't split these messages and I can't wait around until the buffer is large enough again to continue.

Thanks!

[igrr]

I think you are looking at Ethernet library. W5100 is a chip which is used in Arduino Ethernet shield. It doesn't have anything to do with WiFi stack. This library supports a use case when you plug W5100 into ESP's SPI port and use it to make an Ethernet connection.

For WiFi, you need to look at WiFiUdp.cpp, UdpContext.h, and the underlying UDP implementation in LwIP stack, udp.c.

[dogmaphobic]

You're right. I had done a global search (all files) and bumped into that. I will have to go back and take a better look at it.

[devyte]

@d-a-v does this make sense in view of #3362 ?