ERROR Can't create pipe (Too many open files)

[jmutanen]

When I run modbus example (Creating master device) multiple times in a row on my Raspberry Pi I got finally an error while creating new master context:

ERROR Can't create pipe (Too many open files)

I use createConRtu for con. It looks like some resources are not freed in the close or free functions?

https://www.npmjs.com/package/modbus#creating-master-device-client

[asfyra]

I have exactly the same problem running the package on a raspberry pi.

[cprice26]

I am also having this problem after the nodejs server runs for a few minutes.

[jmutanen]

I quickly looked to the code and it seems that two file descriptions (ctx_mt->mtp_r and ctx_mt->mtp_w) opened in modbus-rtu.c:1097 are never closed.

int mtp[2]; if (pipe(mtp) == -1) { fprintf(stderr, "ERROR Can't create pipe (%s)\n", strerror(errno)); modbus_free(ctx); return NULL; } ctx_mt->mtp_r = mtp[0]; ctx_mt->mtp_w = mtp[1];

[jmutanen]

I made a fix for this one, pull request created. Fix available in https://github.com/jmutanen/nodejs_libmodbus.

[jmutanen]

There was still one issue. I hade to make one small modification.

nodejs_libmodbus/modbus.js::createMasterRtu and api.Destroy function:

mb.close(ctx); => mb.close_mt(ctx);

Should the same modifications be applied in createMasterTcp api.Destroy function?

[cprice26]

jmutanen,

I did the following:

1. I replaced my existing mt.patch file with yours.
2. I replaced my existing make_libmodbus.sh yours.
3. Then I replaced my modbus.js file with yours.
4. I then re-built running ./make_libmodbus.sh

I still receive the following errors after it runs for few minutes: ERROR Can't create pipe (Too many open files) ERROR createMasterRtu: Too many open files

Did I do something wrong in applying the patches or is there still an issue?

Thank you for your help!

[jmutanen]

Hi,

Did you build the package with node-gyp?

./make_libmodbus.sh && node-gyp configure && node-gyp build

Cheers, -Jussi

[cprice26]

That was the problem. I did not rebuild with node-gyp. Seems to be working fine now. Thanks!