Forward Open bug with T_O_Length > 255

Ethernet/IP compatible library for .NET and LabView implementations

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Forward Open bug with T_O_Length > 255

Forum: General Discussion

Creator: uhggernaut

Created: 2019-10-18

Updated: 2022-04-08

uhggernaut - 2019-10-18

Hi there,

There still seems to be a bug with the forward open implementation. I am unable to get the T->O connection size larger than 255. When it should be 256 the 9th bit never gets set and the size rolls over to zero.
It would be awesome if you could fix it. Thanks!

Wireshark packet 255.png

Wireshark packet 256.png

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Rossmann Engineering - 2019-10-26

Hi, I don't think there is a Bug, because for connection sizes > 255 you have to use "large forward open". Large forward open is already implemented in the Code available at Github.

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huitzilopochtli - 2022-04-08

Hi,

The maximum size that you can set for Forward Open are 9 bits according to the standard which is 511 bytes.

For Large Forward Open are 15 bits. and it is optional to implemented. Not all the EIP devices does it.

I tested with Codesys with a EIP device which I know that Large Forward Open is not implemented.

Last edit: huitzilopochtli 2022-04-08

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