FtpWrite - Write data to a remote file.
int FtpWrite(void *buf, int len, netbuf *nData);
buf A buffer containing the data to be sent to the remote file.
len The number of bytes to be sent from ’buf’.
nData A handle returned by FtpAccess().
FtpWrite() sends data to a remote file. If the file were accessed in
record mode, the necessary conversions are performed.
Returns the number of bytes sent from the user’s buffer or -1 on error.