Packet size in MQTT

Question

Hello I’m using IoLibrary and I have this problem. I’m using w5500 as my chip and I’m a mqtt client who is using iolibrary. Until packet size is less than my socket dedicated volume everything is ok . I can subscribe and get message successfully . But when packet size is more than socket dedicated volume, I receive nothing despite of subscribing this special topic. Maximum socket dedicated volume is 16kb in w5500 chip, but my desired data size is more than 16kb its about 40kb . Please help me solve this problem . what should I do ? Thank you.

irina · Answer

Anything over 40kb per packet is not available on our chip. But if you want to send them sequentially, there is no problem with the code you are currently providing.

irina · Answer

In case of TCP mode, it can send up to 1460byte per packet. Our chips not supports the fragmentation of TCP. Therefore, in order to transmit a lot of data, it is necessary to control the memory. For this part, we recommend that you check the send() / recv() function in the iolibrary that we provide.

kamin · Answer

hello irina thanks for your help. I’m using mqtt protocol . do you have any solution for me ? I will appreciate if you provide me piece of code for receiving a lot of data in mqtt using iolibrary?

irina · Answer

We can support the MQTT example but I don’t know if that code can receive and transmit large amounts of data. This code simply supports MQTT. GitHub GitHub - WIZnet-ioLibrary/W5x00_MQTT: W5x00_MQTT W5x00_MQTT. Contribute to WIZnet-ioLibrary/W5x00_MQTT development by creating an account on GitHub.

kamin · Answer

thanks, but this cant help us. I have questions about details of ioLibrary. would you please connect me with the developer of ioLibrary .

kamin · Answer

we have sent and received large data with w5500 chip successfully by using its registers without iolibrary , but now we are using iolibrary and facing with problem, the issue is we cant receive large data . please provide me the process sequence of receiving large data using iolibrary. unfortunately the GitHub source code you mentioned didn’t help me . please help me overcome this obstacle.