RakNet 63 session limit

Question

I'm using raknet for tcp networking on windows server 2008, it can accept a lot of connections but can't receive packets from all of them: only 63 client's packets can be read.

Here is my receive code:

if (tcpInterface->ReceiveHasPackets())
    {

        for (packet = tcpInterface->Receive(); packet; tcpInterface->DeallocatePacket(packet), packet = tcpInterface->Receive())

        {
            TRACE("tcpInterface->GetConnectionCount(); %d \n", tcpInterface->GetConnectionCount());
            //sNetMgr->ReceivedPacket(packet);
        }
    }