TCP issue with large packet under RTEMS

João Rasta freakforever at
Wed Feb 9 16:36:25 UTC 2011


I'm using RTEMS 4.10 and GRETH MAC in order to exchange data with a client
PC via TCP. I have a LEON-3 based processor architecture. I can successfully
attach the GRETH ethernet driver using the RTEMS driver manager and exchange
small ammounts of data. However, when i need to transfer an image array
(436160Bytes) from the PC to the RTEMS system, the read() call only returns
17508Bytes read instead of 436160Bytes .

The send() directive in the PC side returns the correct number of bytes sent
so the problem must be on the RTEMS side. The read buffer has the correct

1) Is there any programmable limitation related to the number of bytes to
receive? Since i'm using a TCP socket, there is no apparent reason for byte
loss i guess..

2) In what circumstances should read() from a TCP socket return less bytes
than the ones sent?

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