PeerGraphListen function (p2p.h)

Article
10/13/2021

The PeerGraphListen function indicates that a peer graph should start listening for incoming connections.

Syntax

NOT_BUILD_WINDOWS_DEPRECATE HRESULT PeerGraphListen(
  [in] HGRAPH hGraph,
  [in] DWORD  dwScope,
  [in] DWORD  dwScopeId,
  [in] WORD   wPort
);

Parameters

[in] hGraph

Specifies the peer graph to listen on.

[in] dwScope

Specifies the IPv6 scope to listen on. Valid values are identified in the following table. For more information about scope, see Link-Local and Site-Local Addresses.

Value	Meaning
PEER_GRAPH_SCOPE_GLOBAL	Scope includes the Internet.
PEER_GRAPH_SCOPE_SITELOCAL	Scope is restricted to a site, for example, a corporation intranet.
PEER_GRAPH_SCOPE_LINKLOCAL	Scope is restricted to a local subnet.

[in] dwScopeId

Specifies the IPv6 scope ID to listen on. Specify zero (0) to listen on all interfaces of the specified scope.

Note The scope ID zero (0) is not allowed if dwScope is PEER_GRAPH_SCOPE_SITELOCAL or PEER_GRAPH_SCOPE_LINKLOCAL.

[in] wPort

Specifies the port to listen on. Specify zero (0) to use a dynamic port. If zero (0) is specified, use PeerGraphGetNodeInfo to retrieve data.

Return value

Returns S_OK if the operation succeeds. Otherwise, the function returns one of the values identified in the following table.

Return code	Description
E_INVALIDARG	One of the parameters is not valid.
E_OUTOFMEMORY	There is not enough memory to perform the specified operation.
PEER_E_GRAPH_NOT_READY	The graph has never been synchronized. An application cannot listen until the peer graph has been synchronized.
PEER_E_INVALID_GRAPH	The handle to the peer graph is invalid.
PEER_E_NOT_INITIALIZED	The graph must be initialized with a call to PeerGraphStartup—before using this function.

Remarks

To be able to accept direct connections, a node must subscribe to the PEER_GRAPH_EVENT_DIRECT_CONNECTION event.

Before this function can be called, the application must call PeerGraphCreate or PeerGraphOpen.

Note If this is the first time a peer graph is opened, all calls to PeerGraphListen fail until the node connects to and synchronizes with the peer graph.

The application can specify the same port ID for different peer graphs, if all the peer graphs are in the same process.

Examples

The following code snippet shows how to use the PeerGraphListen function.

    // g_hGraph is a handle to the Graph obtained from a previous successful call to PeerGraphCreate or PeerGraphOpen.
    // dwScope should be set to the same scope used to create the graph.  This example assumes the graph was created in the Global scope.
    // g_usPort is the port to use for Graphing.  Use zero to obtain a port dynamically.
    HRESULT hr = PeerGraphListen(g_hGraph, PEER_GRAPH_SCOPE_GLOBAL, 0, g_usPort);

    if (FAILED(hr))
    {
        // Insert your code to handle the error here.
    }
    else
    {
        // Insert your application specific code here.
    }

Requirements

Requirement	Value
Minimum supported client	Windows XP with SP2 [desktop apps only],Windows XP with SP1 with the Advanced Networking Pack forWindows XP
Minimum supported server	None supported
Target Platform	Windows
Header	p2p.h
Library	P2PGraph.lib
DLL	P2PGraph.dll

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