Server sends this message right after successful handshake with a client. For web socket connection handshake happens automatically and transparently between browser and the server. For raw TCP/IP connection, handshake happens when client sends C2S::GM message. As a reply server sends S2C::SERVER_INFO message to share information about server version.
struct s2c_server_info_t {
char type; // MSG_S2C_SERVER_INFO
char major; // Server major version (season #)
char minor; // Server minor version
};