While experimenting with a UDP server that runs on esp32, I found that the size of the received packet is limited to 1500 bytes: 20 (IP header) + 8 (UDP header) + 1472 (data), (although in theory UDP as if can support packets data up to 64K). This means that in order to transfer a larger amount of data, the client must split it into several chunks and send them one after the other, and on the server side, this data will need to be restored. I think that the overhead of such a solution will be quite high. I also know that Toit provides TCP/IP connection. Naturally, the packet size is also limited in the case of TCP/IP. This is 64K (65535 bytes). Does Toit have any additional restrictions on the TCP/IP connection, or 64K value is fact also for Toit?
As described in this question/answer, it's a matter of avoiding packet fragmentation. Sending packages above this size will force the system to split them up into multiple fragments of size MTU, with each of them being individually unreliable. As memory is already very limited on embedded systems, sending large (> MTU) packages where all fragments has to arrive before it can be processed, can be very unfortunate for the overall application behavior as it can time out or go out-of-memory.
Instead the application should look at a streaming pipeline (perhaps even TCP to handle the unreliable aspects as well).
As TCP/IP is a streaming protocol, any sized "packages" can be sent, as they are automatically split into fragments of size MTU. Note that the data is received in "random"-sized packages, though the order of the bytes is fully preserved.