can't open nfs server file ValueError: open failed: Input/output error

[koalaxiu7]

can't open nfs server file
File "/app/server.py", line 44, in init
self.nfs_connect()
File "/app/server.py", line 325, in nfs_connect
a = self.nfs.open('/nfstest.txt', mode='w+')
File "/usr/local/lib/python3.7/site-packages/libnfs/init.py", line 187, in open
return NFSFH(self._nfs, path, mode=mode, codec=codec)
File "/usr/local/lib/python3.7/site-packages/libnfs/init.py", line 81, in init
raise ValueError(_errmsg)
ValueError: open failed: Input/output error

[wood-j]

nfs4?