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Independent clients

  • Article

Applies To: Windows Server 2003, Windows Server 2003 R2, Windows Server 2003 with SP1, Windows Server 2003 with SP2

Independent clients

For the purposes of this documentation, the term Message Queuing server refers to a Windows Server 2003 family computer that has Message Queuing installed. The term Message Queuing client can refer to either an independent client, or a dependent client. Both of these terms are used to describe Message Queuing servers that have particular Message Queuing components installed, and such computers are referred to as having independent client functionality, or dependent client functionality.

Computers defined as running with independent client functionality do not have the following features:

  • They do not have the Routing component enabled, and thus do not have the message routing capabilities of a Message Queuing server with this component.

  • They do not have the Downlevel Client Support component enabled, and thus cannot provide Active Directory access for MSMQ 1.0 clients running on Windows NT 4.0, Windows 98, or Windows 95 computers, or MSMQ 2.0 clients running on Windows 2000.

Message Queuing computers configured with independent client functionality run the Message Queuing service, host queues, send and receive messages, and can operate while disconnected from the network. They do not require synchronous access to a Message Queuing server to send or receive messages, or to query Active Directory. However, if you choose to install an independent client in a workgroup environment or any other environment that does not provide a directory service, such as Active Directory, direct connectivity is required to send messages. Any Windows Server 2003 family computer running Message Queuing and operating in domain mode, including independent clients, can act as a supporting server for dependent clients.

If an independent client is disconnected from the network, it can continue to generate messages destined for other computers. The independent client stores these messages locally and automatically sends them as soon as the network connection is reestablished.

Independent client advantages

The advantages of deploying independent clients in your organization are as follows:

  • They are not dependent on a Message Queuing server to send or receive messages, and synchronous communications with a Message Queuing server are not required.

  • The messaging load can be distributed across several Message Queuing servers by configuring independent clients to use specific Message Queuing servers (in-routing servers and out-routing servers).

  • They support mobility; independent clients can move from site to site.

Mobile usage

Mobile independent clients, such as those installed on laptop computers, can send and receive messages when they move around. When an independent client connects to a new Windows Server 2003 family site, it automatically detects the domain controllers in its new domain and queries the directory service to determine the new site in which it resides. After the new site is established, all messages that were sent to the client while it was disconnected from the network are automatically rerouted from the previous site to the new site. Note that mobile users that run Message Queuing applications while disconnected from the network can place an additional load on the network. This happens when they attempt to send or receive a large number of messages when they reconnect to the network. This temporary load can be transferred to additional Message Queuing servers to prevent reduced performance.

A Message Queuing 3.0 computer that belongs to a Windows NT 4.0 enterprise and is capable of connecting to MSMQ 1.0 controller servers is not capable of automatically revealing its new site. In this case, you can provide the name of the new site either before disconnecting the computer from the network or after reconnecting to the network. Selecting a new site enables your computer to connect to the closest controller server and thus optimizes access to the MQIS database. If you specify the new site before disconnecting from the network, messages sent to the computer while it is disconnected are routed directly to the new site while the computer is en route.

As stated previously, clients can be configured to use Message Queuing servers (in-routing and out-routing servers) for intrasite routing. When such a client moves to a different site, those in-routing or out-routing servers are not used for routing messages in the new site. When the independent client returns to its original site, those same Message Queuing servers are again used for routing messages.

Windows CE usage

A special version of the independent client is also available on handheld and palm-sized computers that are running Windows CE 3.0 or later. Because of capacity requirements and lack of RPC support, the following limitations apply to the Windows CE version of the independent client:

  • No Active Directory support. Windows CE independent clients cannot query Message Queuing servers running on Windows Server 2003 family domain controllers.

  • Limited message routing support.

  • Limited public queue support.

  • No message authentication or encryption. All messages sent to or received by other Message Queuing computers travel as plaintext.

  • No remote retrieval of messages. Messages stored on another Message Queuing computer cannot be retrieved from the Windows CE independent client.

  • No multi-message transactions.

  • No cross-platform support. Messages cannot be sent to computers running other messaging systems.