Windows binaries say "Connection refused" even on connection timeout

When zabbix_sender.dll library fails to connect to Zabbix server due to invalid server IP address, parameter char **result of function zabbix_sender_send_values() contains a truncated 254 bytes long error message "cannot connect to [[10.0.255.1]:10051]: [0x0000274C] ??????? ?????????? ?????????? ???? ???????????, ?.?. ?? ??????? ?????????? ?? ????????? ????? ?? ??????? ????". The message (at least visible part of it) is correct, but it apparently did not fit in 255 bytes long buffer because russian unicode characters take twice more bytes than english unicode characters.