KeepAlive Property

Gets or sets the value of the socket's KeepAlive option.

[Visual Basic]
<DefaultValueAttribute()>
<DescriptionAttribute("Gets or Sets the value of the socket's KeepAlive option.")>
<CategoryAttribute("Socket Options")>
Public Property KeepAlive As Boolean

[C#]
[DefaultValueAttribute()]
[DescriptionAttribute("Gets or Sets the value of the socket's KeepAlive option.")]
[CategoryAttribute("Socket Options")]
public bool KeepAlive {get; set;}

[C++]
[DefaultValueAttribute()]
[DescriptionAttribute("Gets or Sets the value of the socket's KeepAlive option.")]
[CategoryAttribute("Socket Options")]
public: __property bool get_KeepAlive();
public: __property void set_KeepAlive( 
   bool value
);

[C++/CLI]
[DefaultValueAttribute()]
[DescriptionAttribute("Gets or Sets the value of the socket's KeepAlive option.")]
[CategoryAttribute("Socket Options")]
public:
property bool KeepAlive {
   bool get();
   void set (bool value);
}

Return Type

true if packets are to be sent during inactive periods; otherwise, false. The default value is false.

Remarks

When a connection is inactive (data is not being sent or received for a period of time), setting Tcp.KeepAlive to true causes the underlying Socket of the Tcp component to probe the other end of a connection when it has been idle for an allotted amount of time (usually 2 hours).

This property can be used to ensure a connection reset indication occurs during periods of inactivity.

The timeout before keepalives are sent and the interval between keepalive transmissions can be set by editing the system's registry.

1. Find the registry key.

For Windows 95/98/ME:

[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\VxD\MSTCP]

For other Operating Systems:

[HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\Tcpip\Parameters]

2. Create a DWORD value "KeepAliveTime" and set it to the number of milliseconds to wait before sending keep alive packets (the default is 2 hours - 7,200,000 milliseconds).

3. Create a DWORD value (or string value for Windows 98) "KeepAliveInterval" and set it to the time in milliseconds between retransmissions of keepalives, once the KeepAliveTime has expired (the default is 1 second - 1000 milliseconds).

4. Restart Windows for the change to take effect.

Example

The following example demonstrates some of the lesser used Tcp component members.

[Visual Basic]

' Disable UI events.

Tcp1.DoEvents = False



' Enable KeepAlive socket option

Tcp1.KeepAlive = True



' Disable use of Nagle's Algoritm

Tcp1.NoDelay = True



' Read urgent data as normal in-line data.

Tcp1.OutOfBandInline = True



' Allow addresses to be reused

Tcp1.ReuseAddress = True



' Connect

Tcp1.Connect("atropos", 7)



' Send data

Tcp1.Send("test")



' Receive response

Dim seg As Segment = Tcp1.Receive()

[C#]



// Disable UI events.
tcp1.DoEvents = false;


// Enable KeepAlive socket option
tcp1.KeepAlive = true;


// Disable use of Nagle's Algoritm
tcp1.NoDelay = true;


// Read urgent data as normal in-line data.
tcp1.OutOfBandInline = true;


// Allow addresses to be reused
tcp1.ReuseAddress = true


// Connect
tcp1.Connect("atropos", 7);


// Send data
tcp1.Send("test");


// Receive response
Segment seg = tcp1.Receive();

Requirements

Platforms: Windows 98, Windows NT 4.0, Windows Millennium Edition, Windows 2000, Windows XP Home Edition, Windows XP Professional, Windows Server 2003 family

See Also

Requirements

Language

KeepAlive Property

Return Type

Remarks

Example

Requirements

See Also