The connection handshake packet (also known as 'hello packet') is a short packet, which includes the MapleStory version, locale, patch location and the IV's for the AES encryption. This is the only packet that isn't encrypted and is only sent by the server once when a connection is made.
Structure[]
0D 00 || Short for header OR length, most likely 0D 00 or 0E 00 XX XX || Short for MapleStory version XX XX ... || String for MapleStory patch location XX XX XX XX || Unsigned int for AES Client Messages IV XX XX XX XX || Unsigned int for AES Server Messages IV XX || Byte for the MapleStory locale