Product   : ISaGRAF V3

Date        : 7-March-1996

File          : Ethvxwks.Ethernet communication on VxWorks.htm

Subject    : Ethernet communication on VxWorks

Keywords: Ethernet - VxWorks - IDK - recv function -

                  eth_lec_trame function - TATS0ETH.c


For VxWorks one thing has to be changed in file TATS0ETH.c:

the test on the return value of the function 'recv'

should be <= instead of <.

nb = recv....


if (nb <= 0) ...

The problem was found by somebody who made an NT command console program to

demonstrate the use of the ISaGRAF debug link.

If a graceful shutdown sequence on the socket is performed

then that port cannot be used again until the (vxWorks) ISaGRAF target is rebooted.

If an abortive (also known as 'hard') shutdown sequence is performed, then the port can be

re-used as normal.

The problem is caused by eth_lec_trame() (in tats0eth.c). When a socket is

closed gracefully, recv() returns 0 immediately, and will continue to do so

if called again. This causes a spin loop in eth_lec_trame(), with no means

of exit.

If the socket is closed using a hard shutdown, as performed by

the Workbench debugger, then recv() returns ERROR (-1), so the loop is


The problem can easily be corrected by changing the line

if (nb < 0 ) /* error or client socket closed (disconnected) */


if (nb <= 0 ) /* error or client socket closed (disconnected) */

Note that you must have the IDK (ISaGRAF Development Tool) to be

able to make this modification.


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