type of errors that tgl can set:

EPROTO: server returned error for query. Some kinds of error (such as FLOOD_WAIT) tgl can handle by itself, but others it can not. In most cases it means bug in tgl or invalid parameter supplied to method (such as message id). On BSD, EPROTO is not defined. Whenever EPROTO is not #define'd, tgl uses EIO instead.

EINVAL: tgl detected invalid argument supplied before sending query to server. For example user instead of chat or bad msg id. 

ENOENT: tgl received empty response from server. For example when user tried to get message by id

EBADF: tgl can not open file on disk or file is empty

E2BIG: supplied file is too big

ENOTCONN: no public keys available