INetFwMgr::IsPortAllowed method (netfw.h)

Article
10/13/2021

[The Windows Firewall API is available for use in the operating systems specified in the Requirements section. It may be altered or unavailable in subsequent versions. For Windows Vista and later, use of the Windows Firewall with Advanced Security API is recommended.]

Determines whether an application can listen for inbound traffic on the specified port.

Syntax

HRESULT IsPortAllowed(
  [in]  BSTR               imageFileName,
  [in]  NET_FW_IP_VERSION  ipVersion,
  [in]  LONG               portNumber,
  [in]  BSTR               localAddress,
  [in]  NET_FW_IP_PROTOCOL ipProtocol,
  [out] VARIANT            *allowed,
  [out] VARIANT            *restricted
);

Parameters

[in] imageFileName

The image file name of the process listening on the network. It must be a fully qualified path, but may contain environment variables. If imageFileName is NULL, the function determines whether the port is allowed for all applications.

[in] ipVersion

IP version of the traffic. If localAddress is non-NULL, this must not be NET_FW_IP_VERSION_ANY.

[in] portNumber

Local IP port number of the traffic.

[in] localAddress

Either a dotted-decimal IPv4 address or an IPv6 hex address specifying the local address of the traffic. Typically, this is the address passed to bind. If localAddress is NULL, the function determines whether the port is allowed for all interfaces.

[in] ipProtocol

IP protocol of the traffic, either NET_FW_IP_PROTOCOL_TCP or NET_FW_IP_PROTOCOL_UDP.

[out] allowed

Indicates by a value of VARIANT_TRUE or VARIANT_FALSE whether the port is allowed for at least some local interfaces and remote addresses.

[out] restricted

Indicates by a value of VARIANT_TRUE or VARIANT_FALSE whether some local interfaces or remote addresses are blocked for this port. For example, if the port is restricted to the local subnet only.

Return value

C++

Return code	Description
E_ACCESSDENIED	The operation was stopped because of permissions issues.
E_INVALIDARG	The method failed because a parameter was not valid.
E_OUTOFMEMORY	The method was unable to allocate required memory.
E_POINTER	The method failed because a pointer was not valid.

VB

If the method succeeds, the return value is S_OK.

If the method fails, the return value is one of the following error codes.

Return code	Description
E_ACCESSDENIED	The operation was stopped because of permissions issues.
E_INVALIDARG	The method failed because a parameter was not valid.
E_OUTOFMEMORY	The method was unable to allocate required memory.
E_POINTER	The method failed because a pointer was not valid.

Remarks

The INetFwPolicy2::IsRuleGroupEnabled method is generally recommended in place of this method.

The IsPortAllowed method checks whether traffic will be allowed with the current firewall configuration for:

A specific application.
A specific port.
A specific application on a specific port.

In its operation IsPortAllowed considers whether the firewall is currently enabled or disabled, whether the application is allowed in the current profile Exceptions List, whether the port is allowed in the current profile Exceptions List, whether the file and print sharing option has been enabled, and whether the remote administration option has been enabled.

Because of the many factors in determining whether a port is allowed, the more specific information that is given via this method's input parameters, the more likely a clear result with meaningful restrictions will be returned.

Requirements

Requirement	Value
Minimum supported client	Windows Vista, Windows XP with SP2 [desktop apps only]
Minimum supported server	Windows Server 2003 with SP1 [desktop apps only]
Target Platform	Windows
Header	netfw.h
DLL	FirewallAPI.dll; Hnetcfg.dll on Windows XP with SP2