Abstract:
In one embodiment, a method of delivering messages to a user of a user terminal executing a communication client and connected to a packet-based communication network, includes receiving a message at the communication client from the communication network, the message comprising a content portion and a control portion, wherein the content portion comprises information intended for display to the user of the user terminal, and storing the message in a data store at the user terminal. The communication client reads the control portion of the message and extracts data defining a trigger event and a condition. The communication client is monitored to determine whether the communication client state corresponds to the trigger event. Responsive to the communication client state corresponding to the trigger event, the communication client determines whether the condition is met. In the case that the condition is met, the content portion of the message is displayed in the communication client.

Description:
TECHNICAL FIELD 
       [0001]    This invention relates to a message delivery system and method, particularly but not exclusively for use in a packet-based communication system. 
       BACKGROUND 
       [0002]    Packet-based communication systems allow the user of a device, such as a personal computer, to communicate across a computer network such as the Internet. Packet-based communications systems include voice over internet protocol (“VoIP”) communication systems and instant messaging (“IM”) systems. These systems are beneficial to the user as they are often of significantly lower cost than fixed line or mobile networks. This may particularly be the case for long-distance communication. To use a VoIP or IM system, the user must install and execute client software on their device. The client software provides the VoIP or IM connections as well as other functions such as registration and authentication. In addition to voice communication, the client may also provide further features such as video calling. 
         [0003]    One type of packet-based communication system uses a peer-to-peer (“P2P”) topology built on proprietary protocols. To enable access to a peer-to-peer system, the user must execute P2P client software provided by a P2P software provider on their computer, and register with the P2P system. When the user registers with the P2P system the client software is provided with a digital certificate from a server. Once the client software has been provided with the certificate, communication can subsequently be set up and routed between users of the P2P system without the further use of a server. In particular, the users can establish their own communication routes through the P2P system based on the exchange of one or more digital certificates (or user identity certificates, “UIC”), which enable access to the P2P system. The exchange of the digital certificates between users provides proof of the user&#39;s identities and that they are suitably authorised and authenticated in the P2P system. Therefore, the presentation of digital certificates provides trust in the identity of the user. It is therefore a characteristic of peer-to-peer communication that the communication is not routed using a server but directly from end-user to end-user. Further details on such a P2P system are disclosed in WO 2005/009019. 
         [0004]    In contrast to traditional communication systems such as fixed-line or mobile networks, the communication client for a packet-based communication client has a flexible, rich graphical user interface. The graphical user interface is displayed to the user on a display of the personal computer, and permits the communication client to present a large number of features and options to the user. However, it is difficult for the provider of the client software to inform the user of these features in a timely and non-intrusive manner. 
       SUMMARY 
       [0005]    According to one aspect of the present invention there is provided a method of delivering messages to a user of a user terminal executing a communication client and connected to a packet-based communication network, comprising: receiving a message at the communication client from the communication network, the message comprising a content portion and a control portion, wherein the content portion comprises information intended for display to the user of the user terminal; storing the message in a data store at the user terminal; the communication client reading the control portion of the message and extracting data defining a trigger event and a condition; monitoring the communication client to determine whether the communication client state corresponds to the trigger event; responsive to the communication client state corresponding to the trigger event, the communication client determining whether the condition is met; and in the case that the condition is met, displaying the content portion of the message in the communication client. 
         [0006]    Preferably, the condition comprises at least one parameter and at least one respective required value, and the step of determining whether the condition is met comprises reading, for each of the at least one parameters, a current value of the parameter in the communication client and comparing the current value to the respective required value. 
         [0007]    Preferably, one of the at least one parameters is a display count for the message and the respective required value defines a maximum number of times the message should be displayed. Preferably, one of the at least one parameters is a time interval parameter and the respective required value defines a start and end time for displaying the message. 
         [0008]    In one embodiment, the method further comprises the step of the communication client transmitting a request for messages over the communication network. Preferably, the request for messages comprises an identifier of messages stored at the user terminal. Preferably, the request for messages comprises at least one of a version number for the communication client and an identifier of an operating system executed on the user terminal. 
         [0009]    Preferably, the message is received at the communication client in a bundle comprising a plurality of messages. 
         [0010]    In another embodiment, the displayed message comprises a selectable control arranged to cause the communication client to display further information to the user. Preferably, the further information is obtained from the communication network. Preferably, the selectable control is a hyperlink comprising a network address of the further information. 
         [0011]    Preferably, the communication client is a voice over internet protocol communication client. Preferably, the voice over internet protocol communication client is a peer-to-peer communication client. 
         [0012]    According to another aspect of the present invention there is provided a computer program product comprising program code which when executed by a computer implement the steps according to the above-described method. 
         [0013]    According to another aspect of the present invention there is provided a user terminal connected to a packet-based communication network, comprising: a data store; a display; and a processor arranged to execute a communication client, wherein the client is configured to: receive a message from the communication network, the message comprising a content portion and a control portion, wherein the content portion comprises information intended for display to the user of the user terminal; store the message in the data store; read the control portion of the message and extract data defining a trigger event and a condition; monitor the communication client to determine whether the communication client state corresponds to the trigger event; determine whether the condition is met responsive to the communication client state corresponding to the trigger event; and display the content portion of the message on the display in the case that the condition is met. 
         [0014]    Preferably, the client is further configured to transmit a request for messages over the communication network. In one embodiment, the request for messages comprises an identifier of messages stored at the user terminal. In another embodiment, the request for messages comprises at least one of a version number for the communication client and an identifier of an operating system executed on the user terminal. 
         [0015]    Preferably, the message is received at the communication client in a bundle comprising a plurality of messages. 
         [0016]    Preferably, the displayed message comprises a selectable control arranged to cause the communication client to display further information to the user. In one embodiment, the further information is obtained from the communication network. In another embodiment, the selectable control is a hyperlink comprising a network address of the further information. 
         [0017]    Preferably, the data store is a message database. Preferably, the communication client is a voice over internet protocol communication client. Preferably, the voice over internet protocol communication client is a peer-to-peer communication client. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]    For a better understanding of the present invention and to show how the same may be put into effect, reference will now be made, by way of example, to the following drawings in which: 
           [0019]      FIG. 1  shows a P2P communication system. 
           [0020]      FIG. 2  shows an example user interface of a client. 
           [0021]      FIG. 3  shows a detailed view of a user terminal. 
           [0022]      FIG. 4  shows a flowchart for defining and publishing a message. 
           [0023]      FIG. 5  shows the structure of a message. 
           [0024]      FIG. 6  shows the process for a client to fetch a message. 
           [0025]      FIG. 7  shows a flowchart for a client to display a message. 
           [0026]      FIG. 8  shows a message display region in a contact tab of a client. 
           [0027]      FIG. 9  shows a message display region in a dial tab of a client. 
           [0028]      FIG. 10  shows a message display region in a public conversations tab of a client. 
           [0029]      FIG. 11  shows a message display region in a directory tab of a client. 
           [0030]      FIG. 12  shows a message display region displayed during a call. 
           [0031]      FIG. 13  shows example messages displayed in the client. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Reference is first made to  FIG. 1 , which illustrates a P2P communication system  100 . Note that whilst this illustrative embodiment is described with reference to a P2P communication system, other types of communication system could also be used, such as instant messaging systems and other, non-P2P, VoIP systems. A first user of the P2P communication system (denoted “User A”  102 ) operates a user terminal  104 , which is shown connected to a P2P network  106 . Note that the P2P network  106  utilises a communication system such as the Internet, but is illustrated as a separate network in  FIG. 1  for clarity. The user terminal  104  may be, for example, a personal computer (“PC”), personal digital assistant (“PDA”), a mobile phone, a gaming device or other embedded device able to connect to the P2P network  106 . The user device is arranged to receive information from and output information to a user of the device. In a preferred embodiment of the invention the user device comprises a display such as a screen and a keyboard and mouse. The user device  104  is connected to the P2P network  106  via a network interface  108  such as a modem, and the connection between the user terminal  104  and the network interface  108  may be via a cable (wired) connection or a wireless connection. 
         [0033]    The user terminal  104  is running a client  110 , provided by the P2P software provider. The client  110  is a software program executed on a local processor in the user terminal  104 . The user terminal  104  is also connected to a handset  112 , which comprises a speaker and microphone to enable the user to listen and speak in a voice call. The microphone and speaker does not necessarily have to be in the form of a traditional telephone handset, but can be in the form of a headphone or earphone with an integrated microphone, or as a separate loudspeaker and microphone independently connected to the user terminal  104 . 
         [0034]    An example of a user interface  200  of the client  110  executed on the user terminal  104  of User A  102  is shown illustrated in  FIG. 2 . The client user interface  200  displays the username  202  of User A  102  in the P2P system, and User A can set his own presence state (that will be seen by other users) using a drop down list by selecting icon  204 . 
         [0035]    The client user interface  200  comprises a tab  206  labelled “contacts”, and when this tab is selected the contacts stored by the user in a contact list are displayed. In the example user interface in  FIG. 2 , five contacts of other users of the P2P system (User B to F) are shown listed in contact list  208 . Each of these contacts have authorised the user of the client  110  to view their contact details and online presence and mood message information. Each contact in the contact list has a presence status icon associated with it. For example, the presence status icon for User B  210  indicates that User B is “online”, the presence icon for User C  212  indicates that User C is “not available”, the presence icon for User D  214  indicates that User D&#39;s state is “do not disturb”, the presence icon for User E  216  indicates User E is “away”, and the presence icon for User F  218  indicates that User F is “offline”. Further presence indications can also be included. Next to the names of the contacts in pane  208  are the mood messages  220  of the contacts. 
         [0036]    The contact list for the users (e.g. the contact list  208  for User A) is stored in a contact server (not shown in  FIG. 1 ). When the client  110  first logs into the P2P system the contact server is contacted, and the contact list is downloaded to the user terminal  104 . This allows the user to log into the P2P system from any terminal and still access the same contact list. The contact server is also used to store the user&#39;s own mood message (e.g. the mood message of User A  102 ) and a picture selected to represent the user (known as an avatar). This information can be downloaded to the client  110 , and allows this information to consistent for the user when logging on from different terminals. The client  110  also periodically communicates with the contact server in order to obtain any changes to the information on the contacts in the contact list, or to update the stored contact list with any new contacts that have been added. Presence information is not stored centrally in the contact server. Rather, the client  110  periodically requests the presence information for each of the contacts in the contact list  208  directly over the P2P system. Similarly, the current mood message for each of the contacts, as well as a picture (avatar) that has been chosen to represent the contact, are also retrieved by the client  110  directly from the respective clients of each of the contacts over the P2P system. 
         [0037]    Calls to the P2P users in the contact list may be initiated over the P2P system by selecting the contact and clicking on a “call” button  222  using a pointing device such as a mouse. Alternatively, the call may be initiated by typing in the P2P identity of a contact in the field  224 . Referring again to  FIG. 1 , the call set-up is performed using proprietary protocols, and the route over the network  106  between the calling user and called user is determined by the peer-to-peer system without the use of servers. In  FIG. 1 , an illustrative route is shown between the caller User A ( 102 ) and the called party, User B ( 114 ), via other peers ( 116 ,  118 ,  120 ) of the P2P system. It will be understood that this route is merely an example, and that the call may be routed via fewer or more peers. 
         [0038]    Following authentication through the presentation of digital certificates (to prove that the users are genuine subscribers of the P2P system-described in more detail in WO 2005/009019), the call can be made using VoIP. The client  10  performs the encoding and decoding of VoIP packets. VoIP packets from the user terminal  104  are transmitted into the network  106  via the network interface  108 , and routed to the computer terminal  122  of User B  114 , via a network interface  123 . A client  124  (similar to the client  110 ) running on the user terminal  122  of User B  114  decodes the VoIP packets to produce an audio signal that can be heard by User B using the handset  126 . Conversely, when User B  114  talks into handset  126 , the client  124  executed on user terminal  122  encodes the audio signals into VoIP packets and transmits them across the network  106  to the user terminal  104 . The client  110  executed on user terminal  104  decodes the VoIP packets from User B  114 , and produces an audio signal that can be heard by the user of the handset  112 . 
         [0039]    The VoIP packets for calls between P2P users (such as  102  and  114 ) as described above are passed across the network  106  only, and the PSTN network is not involved. Furthermore, due to the P2P nature of the system, the actual voice calls between users of the P2P system can be made with no central servers being used. This has the advantages that the network scales easily and maintains a high voice quality, and the call can be made free to the users. Additionally, calls can also be made from the client ( 110 ,  122 ) using the P2P system to fixed-line or mobile telephones, by routing the call via a gateway  128  to the PSTN network  130 . Similarly, calls from fixed-line or mobile telephones can be made to the P2P system via the PSTN  130  and gateway  128 . 
         [0040]      FIG. 3  illustrates a detailed view of the user terminal ( 104 ) on which is executed client  110 . The user terminal  104  comprises a central processing unit (“CPU”)  302 , to which is connected a display  304  such as a screen, an input device such as a keyboard  306 , a pointing device such as a mouse  308 , a speaker  310  and a microphone  312 . The speaker  310  and microphone  312  may be integrated into a handset  112  or headset, or may be separate. The CPU  302  is connected to a network interface  108  as shown in  FIG. 1 . 
         [0041]      FIG. 3  also illustrates an operating system (“OS”)  314  executed on the CPU  302 . Running on top of the OS  314  is a software stack  316  for the client  110 . The software stack shows a protocol layer  322 , a client engine layer  320  and a client user interface layer (“UI”)  318 . Each layer is responsible for specific functions. Because each layer usually communicates with two other layers, they are regarded as being arranged in a stack as shown in  FIG. 3 . The operating system  314  manages the hardware resources of the computer and handles data being transmitted to and from the network via the network interface  108 . The client protocol layer  322  of the client software communicates with the operating system  314  and manages the connections over the P2P system. Processes requiring higher level processing are passed to the client engine layer  320 . In particular, the client engine layer  320  comprises message manager functionality  324  and a message database  326 . The functionality of these elements will be described in more detail hereinafter. The client engine  320  also communicates with the client user interface layer  318 . The client engine  320  may be arranged to control the client user interface layer  318  to present information to the user via the user interface of the client (as shown in  FIG. 2 ) and to receive information from the user via the user interface. The control of the client user interface  318  will be explained in more detail hereinafter. 
         [0042]    As mentioned, the use of P2P client software permits the inclusion of a large number of features that can be used by the users. However, there is a difficultly in keeping the users informed of these features. Furthermore, it is useful for the P2P software provider to be able to inform the users of promotions that are available, and to give the users feedback in the case of detected problems or errors. 
         [0043]    Error messages and information/help messages can be built into the client (i.e. hard-coded) such that they can be shown to the users as soon as the client is installed and executed on the user&#39;s terminal. However, this has the significant disadvantage that the messages cannot be adapted or changed without the user installing a new version of the client. For example, the P2P software provider may become aware that a particular feature is not being used frequently by the users, because the users are either unaware of its existence or do not understand how to use it. In such cases, hard-coded messages cannot change in order to inform the user of this feature. Similarly, the P2P software provider may begin offering a new promotion or pricing plan, which cannot be communicated through the client until a new version is released with the hard-coded messages. 
         [0044]    There is therefore a need for a dynamic message delivery system that permits the delivery of messages from the P2P software provider to the clients, such that these messages can be displayed by the clients to inform the users of pertinent information. 
         [0045]    A dynamic message delivery system is shown illustrated in  FIG. 1 . Before the process by which the messages are delivered to the clients and displayed to the users is described, the process for creating the messages is outlined. 
         [0046]    The messages are preferably created by an administrator affiliated with the P2P software provider. However, in some embodiments, this role could be fulfilled by a trusted third party. Referring to  FIG. 1 , the administrator  132  operates a user terminal  134  that is connected via a network interface  136  to a network  138  such as the Internet. Executed on a processor of the user terminal  134  is a web browser program  140 . The web browser program  140  is used to view web pages retrieved over the network  138  using the hypertext transfer protocol (“HTTP”). It will be understood that the network  106  used by the P2P system and the network  138  used by the administrator  132  are both, in practice, the Internet. However, they are shown separately in  FIG. 1  in order to distinguish between the information passed over the P2P system (network  106 ) and the information passed over the World Wide Web (network  138 ). 
         [0047]      FIG. 4  shows a flowchart for the process by which the message is created by the administrator  132 . In step S 402 , the administrator executes the web browser program  140  on the user terminal  134 . In step S 404 , the administrator  132  uses the web browser program  140  to log into a back office server ( 142  in  FIG. 1 ) over the network  138 . The back office server  142  displays to the administrator a selection of options that define the structure, content and properties of the message. In S 406 , the administrator selects the options required options to define what the message should display and when it should be displayed. The details of the message structure will be described with reference to  FIG. 5  below. 
         [0048]    Following the selection of the message options, in step S 408 , the administrator selects to save the message. The message is saved by the back office server  142  in a content database ( 144  in  FIG. 1 ). The message is marked as requiring review. The review is an optional stage whereby the message is checked, e.g. for language. This may particularly be needed if translations of the messages into multiple languages are required. In step S 410  and S 412  the process waits for the message to be reviewed. Once the message has been approved, then in step S 414  the message stored in the content DB  144  is marked as ready for publication to the clients. 
         [0049]    The messages that are created are grouped together into “bundles”. Bundles are created to minimise the amount of data that needs to be transmitted to the clients. Specifically, a bundle comprises the set of messages that are different to those messages that are pre-installed with the client. Therefore, the bundle constitutes changes or additions to the messages that the clients already contain. By creating the bundles, only those messages that are not already present in the client are transmitted. Obviously, if only a single message is updated compared to those already installed in the client, then the bundle will comprise only one message. As different versions of the clients will contain different messages when they are installed on the user terminals, different bundles need to be compiled for different client versions. Each bundle is given a unique identifier in order to distinguish between them. Once all the messages in a bundle have been approved, the bundle itself can be approved and can be marked as ready for publication to the clients. 
         [0050]    The process by which the messages are delivered to the clients is described in detail with reference to  FIG. 6  hereinafter. 
         [0051]    Reference is now made to  FIG. 5  which illustrates the detailed structure of the messages created by the above-described process and stored in the content DB  144 . The message  500  comprises a message type field  502  which defines a particular category for the message. For example, the message type field  502  can define that the message is an information message, a user tip message or a promotion message. The type of message can be used to determine how the message is displayed in the client, for example background colours and icons can be displayed according to the type of message. The message  500  also comprises a message content field  504 , which contains the actual information to be displayed to the users of the clients. The message content  504  can comprise text, images, animation (e.g. flash animation) or a combination of the above. Example message content will be described hereinafter. 
         [0052]    The message  500  further comprises a trigger  506 . The trigger  506  defines an event that must occur in the client before the message content is displayed to the user of the client. Example triggers include, but are not limited to: 
         [0053]    Making a call from a P2P client to another P2P client; 
         [0054]    Making a call from a P2P client to the PSTN; 
         [0055]    Receiving a call at a P2P client from another P2P client; 
         [0056]    Receiving a call at a P2P client from the PSTN; 
         [0057]    Starting to send a video feed; 
         [0058]    Starting to receive a video feed; 
         [0059]    Making a conference call; 
         [0060]    A date, time or period (e.g. a specific date or every x days); 
         [0061]    A missed call; 
         [0062]    A contact is added to the user&#39;s contact list; 
         [0063]    Viewing a particular UI in the client; 
         [0064]    Starting an IM chat conversation with one party; and 
         [0065]    Started an IM chat conversation with more than one party (called a multichat). 
         [0066]    In addition to the trigger event  506  that must occur for the message to be displayed, the message  500  can also define a condition  508  that must further be satisfied in order for the message to be shown to the user. Example conditions include, but are not limited to: 
         [0067]    The time elapsed since the message was last displayed; 
         [0068]    The value of the user&#39;s account balance for outgoing PSTN calls; 
         [0069]    The date of expiry of credit in the user&#39;s account for outgoing PSTN calls; 
         [0070]    Whether the user has subscribed to receive incoming PSTN calls; 
         [0071]    The date of expiry of the user&#39;s incoming PSTN call subscription; 
         [0072]    Whether the user has subscribed for voicemail; 
         [0073]    The date of expiry of the user&#39;s voicemail subscription; 
         [0074]    The user&#39;s region as defined in their profile; 
         [0075]    A software registry key value; 
         [0076]    The client version number for the user initiating a call; 
         [0077]    The client version number for a user receiving a call; 
         [0078]    The operating system on which the client is executed; 
         [0079]    The user&#39;s privacy settings; 
         [0080]    Has the user ever set a mood message; 
         [0081]    The last date the user&#39;s avatar was changed; 
         [0082]    Has the user ever had an IM chat conversation; 
         [0083]    Has the user ever had an IM multi-chat conversation; 
         [0084]    Has the user ever had a conference call; 
         [0085]    Has the user ever used file transfer; 
         [0086]    The number of contacts in the user&#39;s contact list; 
         [0087]    Has the user set up call forwarding; 
         [0088]    Has the user utilised a contact importing tool; 
         [0089]    Has the user made a video call; 
         [0090]    Has the user performed a video test; 
         [0091]    Has the user made a PSTN call; 
         [0092]    Is the other party in a call authorised by the user; 
         [0093]    Is the other party in a call listed in the user&#39;s contact list; 
         [0094]    The value of the audio gain level on the user&#39;s microphone; 
         [0095]    The current call duration; 
         [0096]    The currently viewed tab in the client UI; 
         [0097]    The client&#39;s current CPU usage; 
         [0098]    The current value of packet loss for a call; 
         [0099]    The current roundtrip value for a call; 
         [0100]    The currently available voice bandwidth; 
         [0101]    The currently available video bandwidth; 
         [0102]    Is the current call relayed over multiple peers; 
         [0103]    The destination country of an outgoing PSTN call; 
         [0104]    The originating country of an incoming PSTN call; 
         [0105]    The amount of credit spent by the user today, this month, this year; 
         [0106]    The language is the client in; and 
         [0107]    The P2P identity (username) of the user. 
         [0108]    Therefore, the trigger  506  defines the event that causes a particular condition  508  to be checked. The condition  508  in the message defines a value (e.g. a number, Boolean value or string) that must be checked against a certain property within the client before the display of the message can proceed. Furthermore, multiple conditions can be defined, such that more than one of the above-listed conditions must be met in order for the message to be displayed. Optionally, no condition can be set, such that only the trigger  506  is required in order for the message to be displayed. 
         [0109]    The message  500  also comprises a link action field  510 . The link action  510  defines the action that is taken by the client when the user clicks on a certain part of the message using the pointing device (e.g. a certain word, sequence of words or image). The link action  510  can define that the client executes a web browser program, which navigates to a certain webpage. Alternatively, the link action  510  can perform an action within the client itself (e.g. opening an option window, displaying the user&#39;s profile etc). 
         [0110]    A recycle field  512  is present in the message  500 , which defines a set number of times that the message content  504  should be displayed. Even if the message has triggered ( 506 ) and met the condition ( 508 ) it will only be displayed if the number of times it has been displayed previously does not exceed the recycle value  512 . Therefore, the recycle value  512  ensures that a given message will only be shown a certain number of times, thereby preventing it from becoming annoying for the users. The recycle value  512  can also be set such that a message can be displayed an indefinite number of times. 
         [0111]    The message  500  further comprises start and end date values  514 . The start and end date values  514  define a time interval during which the message should be displayed. This allows messages to only be displayed over a certain period, which is useful, for example, for time-sensitive marketing campaigns. However, the values for the start and end dates can be set such that the messages are always able to be displayed regardless of the date. 
         [0112]    The message  500  also comprises a display location  516  for the message in the user interface of the client. Example display locations are illustrated in more detail with reference to  FIGS. 8 to 12 . Furthermore, the message  500  comprises a priority field  518 . The priority field  518  defines a priority level for the message in question, such that if the client attempts to display two or more messages in the same location at the same time, then only the message with the highest priority is displayed. 
         [0113]    Therefore, at this point in the process a message has been created by the administrator  132  (as illustrated with reference to  FIG. 4 ) comprising the properties described above with reference to  FIG. 5 , and is stored in the content DB  144 . Note that the administrator can create a plurality of messages, each of which is stored in the content DB  144 . 
         [0114]    The process by which the messages are delivered to the clients is now described with reference to  FIG. 1  and  FIG. 6 . The clients ( 110 ,  122 ) are configured to periodically check whether new messages are available to be downloaded. The message manager  324  (as illustrated in  FIG. 3 ) is responsible for triggering the periodic check for new messages. The periodicity of the message checking can be defined in order to balance the requirements of rapidly delivering new messages against the consequential network and server load. For example, the message checking period can be every 14 days, although any time period may be used. In order to prevent all the clients in the P2P system simultaneously attempting to retrieve messages, each client independently maintains its own timer of when messages were last retrieved. Therefore, as the users install and execute clients at different times, this ensures that the message retrieval is distributed over time, thereby reducing peak network loading. 
         [0115]    Referring to  FIG. 6 , in step S 602  the client ( 110 ,  122 ) sends a “request content” message via the network interface ( 108 ,  123 ) over the P2P system. The “request content” message contains an identifier of the bundle of messages currently held by the client, which allows the message delivery system to determine which messages need to be provided to the client. The “request content” message also comprises the software version number for the client and the operating system used on the user terminal. This information is provided because different bundles of messages are compiled for different operating systems and client versions. 
         [0116]    The “request content” message is transmitted from the client to a proxy server  146  over the P2P system. The function of the proxy server  146  is to provide an interface between the peers of the P2P system and backend systems. In particular, the proxy server  146  authenticates users of the P2P system to ensure that they are allowed to have access to the backend systems. 
         [0117]    Providing the client can be authenticated, the proxy server  146  forwards the “request content” message to a message server  148  in step S 604 . The message server  146  acts as the interface to the content DB  144 , and handles the delivery of messages to the clients. Multiple message servers can be utilised in practice, in order to handle the load from a large number of clients requesting content. 
         [0118]    The message server  148  reads the information regarding the software version, operating system and current message bundle ID from the “request content” message, and determines whether newer messages need to be sent to the client. The message server  148  compares the bundle ID for the most recent bundle for the given operating system and software version to the bundle ID from the client. If a newer bundle of messages exists then the message server prepares to send this to the client. If the client already has the latest bundle (i.e. no existing messages have been changed or new ones added since either the client was installed or since the last time the client requested messages from the message server) then the process stops without messages being transmitted to the client. 
         [0119]    Presuming that a newer bundle exists, the message server  148  requests the newer bundle from the content DB  144  in step S 606 , and in step S 608  the newer message bundle is returned to the message server  148 . Note that, in preferred embodiments, the message server  148  can also comprise a cache element  150 , which is used to maintain a local cache of the most recent and commonly requested bundles. This can be advantageously utilised to avoid the need to fetch the bundle from the content DB  144 , thereby reducing the load on the database. 
         [0120]    In step S 610 , the message bundle is transmitted from the message server  148  to the proxy server  146 . The proxy server  146  then transmits the message bundle to the client  110 ,  122  over the P2P system in step S 612 . The client then installs the message bundle. The new message bundle can add new messages to the client, as well as make changes to existing messages or delete messages. Once the message bundle is installed, the current bundle ID held at the client is updated. The message bundle is received by the message manager  324  in the client and stored in the message DB  326  in the client  110  as illustrated in  FIG. 3 . 
         [0121]    In preferred embodiments, statistics about the messages displayed in the clients are also collected in step S 614 . For example, a set of statistics can be collected for each message, which include: a message identifier; the total number of times the message was displayed; the total number of times the user closed the message; the total number of times a link in the message is clicked on; and the total amount of time, in seconds, that the message was displayed. Different statistics requirements can be defined for different messages, and these statistics requirements can be pre-set in the installed client, or can be communicated to the client along with the bundle of messages. 
         [0122]    The statistics collected by the client are reported back to the message server  148  periodically by the client. For example, the client can be arranged to report statistics every four hours. When a time period has passed such that the client needs to report statistics, then the statistics are collated and transmitted in S 616  to the proxy server  146 , and forwarded to the message server  148  in S 618 . The message server  148  then stores the statistics in the statistics DB  152  in step S 620 . The steps of S 616  to S 620  are repeated whenever the period for reporting statistics expires. 
         [0123]    Reference is now made to  FIG. 7 , which illustrates the process by which messages received at the client are interpreted and displayed. In step S 702 , the client  110  is executed on the user terminal  104  of the user  102 . In step S 704 , the message manager  324  of the client  110  reads the messages stored in the message DB  326 . In step S 706 , the message manager  324  extracts the message properties from the messages, specifically those properties described above with reference to  FIG. 5 , including the trigger, conditions, recycle value, start and end dates and priority. The message manager  324  can then begin monitoring the client  110  behaviour to determine whether to display the message. 
         [0124]    In step S 708 , the message manager  324  starts monitoring the triggers defined in the message. Example triggers were outlined hereinabove. If, in step S 710 , the event defined by the trigger has not yet occurred, then the message manager  324  continues monitoring in S 708 . Alternatively, if the trigger event has occurred, then in step S 712  the conditions defined by the message are analysed. Example conditions were described hereinbefore. Typically, the conditions define a value that needs to be compared against a property within the client. The message manager  324  performs this comparison to determine if the condition is met. Note that multiple conditions may be defined in the message, which must all be met, or a null condition defined which is always met by default. 
         [0125]    If the conditions are not met, then in step S 714  the message manager  324  ceases to process the current message in question, and returns to monitoring triggers in step S 708  for the display of future messages. Alternatively, if the conditions are met, then in step S 716  the message manager  324  checks the number of times that the message in question has been displayed. If it is found in step S 718  that this exceeds the recycle value for this message, then the message is not displayed, and the message manager returns to monitoring triggers in step S 708 . If, however, step S 718  finds that the recycle value has not been exceeded, then the process proceeds to step S 720 . 
         [0126]    In step S 720 , the message manager  324  checks the start and end date values for this message. As mentioned before, these values define a time interval during which the message should be displayed. Therefore, in step S 720 , the message manager compares the current date to the start and end dates, to determine if the current date falls within them. If in step S 722  the current date is not within the start and end dates, then the message display should be skipped and the message manager  324  returns to monitoring the triggers in step S 708 . 
         [0127]    If the message is to be displayed (i.e. the current date is within the start and end dates), then in step S 724  it is checked whether another message is already displayed at this display location, and if so, the priority levels of the message are compared. In step S 726 , if the priority level of the current message is lower than another message already being displayed, then the current message is not displayed and step S 708  is returned to. However, if another message is not being displayed at the display location, or the current message has a higher priority, then in step S 726  the message display is not skipped, and in the step S 728  the message is displayed in the UI of the client  110 . More details on the display of the message in the client is provided with reference to  FIGS. 8 to 13  below. Finally, in step S 730 , the count of the number of times the message in question has been displayed is incremented, before the message manager  324  returns to monitoring the triggers in step S 708 . 
         [0128]    The above process is obviously performed for every message that is stored in the bundles in the message DB  326 . It should also be noted that the monitoring, triggering and display of messages happens in parallel for all messages in the client. Therefore, more than one message can be triggered and displayed in the client at one time. 
         [0129]    Reference is now made to  FIGS. 8 to 12 , which illustrates example locations where the messages can be displayed in the client  110 . As mentioned with regards to  FIG. 5 , the messages define a UI display location ( 516 ) which determines where the message is displayed. 
         [0130]      FIG. 8  shows the user interface of the client  110  when displaying the contact list tab  206 , as described above with reference to  FIG. 2 . However, in the case of  FIG. 8 , there is a placeholder  802  for a message to be displayed below the contact list. The message placeholder  802  comprises a close button  804  that removes the message from the display, thereby reverting the client to the form shown in  FIG. 2 . 
         [0131]      FIG. 9  shows the UI of the client  110  when the tab named “call phones”  902  is selected. This tab  902  displays a keypad  904 , allowing the user to enter a telephone number to call. This tab  902  shows an example message display location  906  with a close button  908  as described above.  FIG. 10  shows the UI of the client when the tab labelled “live”  1002  is selected. This tab  1002  displays a list  1004  of ongoing and upcoming public conversations that can be joined by the user. This tab  1002  also displays an example message location  1006  with a close button  1008 . 
         [0132]      FIG. 11  illustrates the UI of the client  110  when the tab labelled “SkypeFind”  1102  is selected by the user. This tab  1102  displays a directory service with fields  1104  for searching for businesses. This tab  1102  displays an example message location  1106  with a close button  1108 .  FIG. 12  shows the tab displayed to the user of the client  110  when a call is in progress. In this case, User A  102  is in a call with User B 114 . The call tab  1202  displays information  1204  about the user being called. An example message location  1206  with a close button  1208  is shown at the bottom of the tab. 
         [0133]    Reference is now made to  FIG. 13 , which illustrates a set of example messages that can be displayed in the UI locations described previously. 
         [0134]    Message  1302  is a message displayed in the call tab  1202  as shown in  FIG. 12 . This message indicates to the user that the client  110  cannot detect any sound on the microphone, and hence there may be a problem with the audio settings. The trigger for this message is making a call (of any type), and the condition is the audio gain level on the microphone. The link in the message (i.e. the link action  510  from  FIG. 5 ) takes the user to the audio settings of the client  110  (i.e. a location internal to the client). 
         [0135]    Message  1304  is a message displayed in the contacts tab  206  shown in  FIG. 8 . The message prompts the user to sign up for a voicemail service. The trigger for this message is a missed call at the client, and the condition is that user has not subscribed to voicemail. The link takes the user to an internet page where they can subscribe to the voicemail service. 
         [0136]    Message  1306  is a message displayed in the call phones tab  902  shown in  FIG. 9 . This message informs the user that they need to purchase credit in order to make calls to the PSTN network. The trigger is the user viewing the call phones tab  902 , and the condition is the user&#39;s credit balance is zero. The link action takes the user to an internet page where they can purchase credit. 
         [0137]    Message  1308  is a promotional message displayed in the contacts list tab  206  shown in  FIG. 8 . This message promotes a service whereby the user can purchase a telephone number to allow PSTN users to call their VoIP client. The trigger for this message is time-based, such that it is displayed on a specified number of days. The condition is that the user has not already signed up for this service—i.e. it is not desirable to promote a service the user already has. The link takes the user to an internet page where they can subscribe to the service. 
         [0138]    Message  1310  is a message displayed in the call tab  1202  shown in  FIG. 12 . If the user was making a PSTN call (trigger) and the balance of his account goes to zero (condition) then the message is displayed. The links display webpages for the user to buy more credit and to set up an automatic credit recharging system. 
         [0139]    Message  1312  is a promotional message displayed in the live  1002  or SkypeFind  1102  tabs in  FIG. 10  or  11  respectively. This message includes images as well as text. The message promotes a subscription service. The trigger is time-based, and the condition is that the user has not already subscribed to the service. The link displays a webpage in which the user can subscribe to the service. 
         [0140]    Message  1314  is displayed in the call tab  1202 . The trigger is that the user is making a call to a PSTN number. There is no condition applied to this message. The message notifies the user that the call would be free if the other party also used the VoIP service, and the link takes the user to a webpage where the user can invite the other party to join the VoIP service. 
         [0141]    Therefore, as shown with the examples above, the messages displayed in the client are relevant to the particular user of the client, due to using triggers and conditions that are dependent upon actions occurring within the client itself. 
         [0142]    While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.