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udpethernetdatagramlwiptms570

How to send 2MB of data through UDP?

I am using TMS570LS3137 (DP84640 Phy). Trying to program UPD(unicast) using lwip to send 2MB of data. As of now i can send upto 63kb of data. How to send 2MB of data at a time. UDP support upto 63kb of transmission only, but in this link https://stackoverflow.com/questions/32512345/how-to-send-udp-packets-of-size-greater-than-64-kb#:~:text=So%20it's%20not%20possible%20to,it%20up%20into%20multiple%20datagrams. They have mentioned as "If you need to send larger messages, you need to break it up into multiple datagrams.", how to proceed with this?

Solution

  • Since UDP uses IP, you're limited to the maximum IP packet size of 64 KiB generally, even with fragmentation. So, the hard limit for any UDP payload is 65,535 - 28 = 65,507 bytes.

    I need to either

    • chunk your data into multiple datagrams. Since datagrams may arrive out of sending order or even get lost, this requires some kind of protocol or header. That could be as simple as four bytes at the beginning to define the buffer offset the data goes to, or a datagram sequence number. While you're at it, you won't want to rely on fragmentation but, depending on the scenario, use either the maximum UDP payload size over plain Ethernet (1500 bytes MTU - 20 bytes IP header - 8 bytes UDP header = 1472 bytes), or a sane maximum that should work all the time (e.g. 1432 bytes).
    • use TCP which can transport arbitrarily sized data and does all the work for you.