Using the ftpc client

Hello everyone ！
After compiling the FTP client program ftpc on a NuttX system and burning it onto a board, I set up an FTP server on a PC and attempted to connect to it from the board. After successfully logging in to the server, every time I entered the 'ls' command, I received an error. Upon debugging, I found that fopen was returning error code 22, which indicates that the file does not exist or the permissions are insufficient. However, I confirmed that the folder exists and has read/write permissions because I tested the 'put' and 'get' commands and was able to upload and download files successfully. Your team's extensive development experience is greatly appreciated - can you offer any suggestions for this issue?
error as follows:
ftpc_listdir: ERROR: Failed to create ftptest/TMP10.dat: 22
nfc> ls failed: 22
pwd
fptc_getreply: Reply: 257 "/home" is the current directory
nfc> PWD: /home"
cd ftptest
fptc_getreply: Reply: 250 Directory successfully changed.
fptc_getreply: Reply: 257 "/home/ftptest" is the current directory
pwd
fptc_getreply: Reply: 257 "/home/ftptest" is the current directory
nfc> nfc> PWD: /home/ftptest"
ls
ftpc_listdir: ERROR: Failed to create ftptest/TMP10.dat: 22
nfc> ls failed: 22
ls
ftpc_listdir: ERROR: Failed to create ftptest/TMP10.dat: 22
nfc> ls failed: 22