C++ Code

    static void SendWorldRWMessage(const char* text, WorldSession* self)
    {
        uint32 textLen = (uint32)strlen((char*)text) + 1;

        WorldPacket data(textLen + 40);
        data.Initialize(SMSG_MESSAGECHAT);

        data << uint8(CHAT_MSG_RAID_WARNING) << uint32(LANG_UNIVERSAL);
        data << (uint64)0 << (uint32)0 << (uint64)0;
        data << textLen << text << uint8(0);

        sWorld->SendGlobalMessage(&data, self);
    }

-- Eluna Lua Code
-- [2] Handle Sysmsg Command
function Commands.sysmsg(player, p)
    msg = p
    textLen = string.len(msg) + 1
    players = GetPlayersInWorld(2, false)

    SMSG_MESSAGECHAT = 150
    CHAT_MSG_RAID_WARNING = 41

    for k, v in pairs (players) do
        local data = CreatePacket(SMSG_MESSAGECHAT, textLen + 40);
        data:WriteUByte(CHAT_MSG_RAID_WARNING)       -- chat type
        data:WriteULong(0)                          -- lang universal
        data:WriteGUID(player:GetGUID())            -- uint64 sender guid
        data:WriteULong(0)                          -- uint32 some flags
        data:WriteGUID(0)                           -- uint64
        data:WriteULong(textLen)                    -- text length
        data:WriteString(msg)                       -- text
        data:WriteUByte(0)                           -- uint8
        print(data)
        v:SendPacket(data)
    end
end