When selecting a port, do not choose a reserved port. The port is specified as a DWORD, although the port number is limited to 65535 (2 bytes) and is used in host byte order. Hr = pAddress->AddComponent(DPNA_KEY_PORT, &dwPort, sizeof(dwPort),DPNA_DATATYPE_DWORD) In the following example, port 12345 is selected. Set a port by calling the IDirectPlay8Address::AddComponent method. Note Ports are not used for serial or modem service providers.

For more information about configuring game ports when players are behind NAT devices, see Network Address Translation, Firewalls, and Proxies. Your application should choose a default port but allow users to override that port in case it is already in use. So, if three computers sharing the same IP address were running the same application, each application would be bound to a different port, allowing messages to be delivered to the correct computer and application.Īlso, if you specify a port, you don't need to use DPNSVR, which makes NAT device administration easier for users. In cases where computers are behind a Network Address Translation (NAT) device and sharing a single public IP address, the port not only specifies the application but also the computer on which the application is running. Each message received would have a port number in its address so that it could be passed to the correct application. So if a user were playing a networked game, sending e-mail, and downloading files at the same time, each application would be bound to a different port. Microsoft® Windows® allows only one application per port. In cases where each computer has a unique IP address, the port specifies the application running on the computer. Ports are an important part of addressing for Internet Protocol (IP) and Internetwork Packet Exchange (IPX) service providers. This topic explains how to select a game port.

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