Abstract:
Arrangements for forwarding content from a message storage server to a content sharing server of a Converged IP Messaging (CPM) system are described. An HTTP PUT request is issued by a user/client to the content sharing server, with the request identifying the location of the content on the message storage server. In response to the HTTP PUT request, the content sharing server issues a request, such as an IMAP download request, to the message storage server (either directly or via an intermediary). In response, the message storage server provides the content, without that content being sent to the user device.

Description:
TECHNOLOGICAL FIELD 
     The invention relates to copying or moving content between servers, in particular, but not exclusively, to copying content between servers storing different types of communication data, including multimedia files. 
     BACKGROUND 
     Modern mobile communication devices are used for a wide range of purposes in addition to traditional telephony. For example, it is known to use instant messaging or email to send messages that include multimedia objects such as images, audio files and video clips. Such messages often include large amounts of data that a user may wish a network to store independently of the messages they were originally attached to. 
     The Open Mobile Alliance (OMA) is developing a Converged IP Messaging (CPM) specification that provides for the convergence of multi-media communication services. The Open Mobile Alliance publishes much of its work on its website (www.openmobilealliance.org). 
       FIG. 1  shows a system, indicated generally by the reference numeral  2 , comprising a client device  4  and a central system  6 . The client device  4  includes a message and media storage client  8 . The central system  6  includes a message and media storage server  10 . The client device  4  may be a CPM-enabled device and the central system  6  may be a CPM system. 
     The message and media storage server  10  provides management and storage functions for messages and other media and is used, for example, to store users&#39; multimedia data. The message and media storage client  8  manages a particular user&#39;s resources at the server  10  and also manages the resources stored locally at the client device  4 . 
     The message and media storage server  10  may be one component or consist of two components, one storing messages and another one storing media. The same can hold for the client side, i.e., it can host a message storage client and a media storage client. 
     Data stored in the message and media storage server  10  can be classified in two different ways:
         1. Message-like contents (such as CPM messages, CPM conversations, and CPM session histories, including their attachments); and   2. Unstructured contents, e.g. plain binary files (of any type).       

     In some circumstances, a user may wish to transfer an attachment of a message from an area storing message-like contents (including the said attachment) to an area containing plain binary files. This may, for example, be done when a user is no longer interested in the whole message, but would like to keep the attachment. For example, if a user receives a message including an image as an attachment, the user may wish to copy the image to a separate location and then delete the original message. 
       FIG. 2  is a flow chart  20  showing, in broad terms, how such an attachment may be transferred. The flow chart  20  includes a first step  22  in which the attachment is downloaded from the message and media storage server  10  to the client  4 . Next, at step  24 , the attachment is uploaded from the client  4  to the area of the server  10  that stores plain binary files. 
     The transfer of data via the client device  4  involves two over-the-air data transmissions. In the event that the end file is not stored at the client device  4 , these over-the-air transmissions represent an unnecessary use of network resources. 
     The present invention seeks to address at least some of the problems outlined above. 
     BRIEF SUMMARY 
     In one exemplary embodiment, a method of forwarding content is provided. The method may comprise: issuing a request to a first server, wherein the request requests that content at a second server be forwarded to the first server and wherein the request includes an indication of a location of the content on said second server; issuing a content access request from the first server to the second server; and forwarding said content from said second server to said first server in response to the content access request. The request issued to the first server may be issued by a user. The content may be multimedia data, such as image, audio or video data. 
     In another exemplary embodiment, a method of forwarding content is provided. The method may comprise: receiving a request to copy content (for example from a user, a user device, or a client) at a first server, the request to copy content requesting that content from a second server be provided to said first server, the request to copy content including an indication of a location of the content on the second server; issuing a content access request from the first server to the second server; and receiving said content at said first server in response to the content access request. The content may be multimedia data, such as image, audio or video data. 
     In a further exemplary embodiment, a method of forwarding content is provided. The method may comprise receiving a content access request from a first server (e.g. a content sharing server) at a second server (e.g. a message storage server), the content access request including an indication of a location of the content on the second server; and forwarding said content from said second server to said first server in response to the content access request. The content may be multimedia data, such as image, audio or video data. 
     In another exemplary embodiment, an apparatus is provided. The apparatus may provide a first server and a second server, wherein: the first server is adapted to issue a content access request to the second server in response to receiving a request to copy content (for example from a user, a user device, or a client), wherein the request to copy content includes an indication of a location of content stored on the second server; and the second server is adapted to provide said content to said first server in response to the content access request. 
     In yet another exemplary embodiment, an apparatus is provided. The apparatus may provide a first server (such as a content sharing server) adapted to: receive a request to copy content, the request to copy content requesting that content at a second server be provided to the first server, the request to copy content including an indication of a location of the content on the second server; issue a content access request to the second server; and receive said content in response to the content access request. 
     In a further exemplary embodiment, an apparatus is provided. The apparatus may provide a first server (such as a content sharing server). The first server may comprise: means for receiving a request to copy content (for example from a user), the request to copy content requesting that content at a second server be provided to the first server, the request to copy content including an indication of a location of the content on the second server; means for issuing a content access request to the second server; and means for receiving said content in response to the content access request. 
     Thus, the present invention enables a user to request that content at a second server (such as a message storage server of a CPM system) be provided to a first server (such as a content sharing server of a CPM system), without that content being passed via the user device. In many forms of the invention, the original content at the second server is retained. 
     The first server may store the content received from the second server. Thus, content can be copied from the second server to the first server in response to the request to copy content, without the user needing to receive the content. The content may be deleted from the second server, if desired. 
     The request to copy content may be an HTTP PUT request. In one particular form of the invention, the request to copy content is an HTTP PUT request with content reference. Other formats for the request to copy content are possible, including non HTTP formats. IMAP is one such alternative. 
     The indication of the location of the content on the second server included in said request to copy content may be provided as an IMAP uniform resource indicator. 
     The content access request issued by the first server to the second server may take the form of an IMAP request; for example, the content access request may include an IMAP uniform resource indicator indicating the location of the content on the second server. Alternatively, the content access request may take the form of an HTTP request, such as an HTTP GET request. Again, other formats are possible, such as requests in accordance with FTP and gopher protocols. 
     In some embodiments of the invention, the requested content is forwarded directly from the second server to the first server. In other forms of the invention, the requested content is forwarded from the second server to the first server via an intermediary, such as an adapter. The adapter may take the form of a separate server. Alternatively, the adapter may be provided as part of the first server. By way of example, the requested content may be forwarded from the second server to a dedicated resource of the first server and may then be further transferred within the first server. The content access request sent by the first server to the second server may be sent via the said adapter. 
     The location of the content on the second server may be identified by a base uniform resource locator in combination with a second uniform resource locator. In some forms of the invention, the request from the user received at the first server includes the base uniform resource locator and the second uniform resource locator. In some other forms of the invention, the request from the user received at the first server includes the second uniform resource locator and the first server provides the base uniform resource locator. 
     The request to copy content received at the first server may include a base uniform resource locator and a second uniform resource locator. The base uniform resource locator may refer to a resource on the first server; in such an arrangement, the content access request may include an HTTP GET request issued to the resource and the resource may issue an IMAP request to the second server. Alternatively, the base uniform resource locator may refer to a resource on the second server; in such an arrangement, the content access request may include an HTTP GET request issued by the first server to the resource on the second server. In a further alternative, the base uniform resource locator may refer to a resource on a third server; in such an arrangement, the content access request may include an HTTP GET request to the resource on the third server and the resource may issue an IMAP request to the second server. 
     In some embodiments of the invention, the first server is an HTTP server. Other server types are possible. The first server may be a WebDAV server. Further, other non-HTTP servers (such as an IMAP server) are possible. 
     In some embodiments of the invention, the second server is an IMAP server. Again, other server types are possible. For example, the second server may be an HTTP server. In some embodiments of the invention, both the first and second servers are HTTP servers. 
     The first server may take the form of a content sharing server. The second server may take the form of a message storage server. The first and second servers may form part of a Converged IP Messaging (CPM) system. According to some aspects of the invention, a file is created or replaced at a content sharing server using the content downloaded from said message storage server. 
     In another exemplary embodiment, a system, such as a converged IP messaging system, is provided. The system may comprise a content sharing server and a message storage server, wherein: the content sharing server is configured to receive a request to copy content (for example from a user) requesting that content at the message storage server be provided to the content storage server, the request to copy content including an indication of a location of the content on the message storage server; the content sharing server is configured to issue a content access request to the message storage server; and the message storage server is configured to provide the content to said content sharing server in response to the content access request. The system may include any of the aspects of the invention described above. 
     In another exemplary embodiment a computer program product is provided. The computer program product may be configured to: receive a request to copy content (for example from a user), the request to copy content requesting that content at a server be provided to the computer program product, the request to copy content including an indication of a location of the content on the server; issue a content access request to said server; and receive said content at said computer program product in response to the content access request. The computer program product may include a computer readable medium. The computer program product may include any of the features of the invention described above. 
     In another exemplary embodiment a computer program product is provided. The computer program product may be configured to: receive a request to copy content from a user, the request to copy content requesting that content be forwarded from a second server to a first server, the request to copy content including an indication of a location of the content on the second server; issue a content access request to said second server; provide said content to said first server in response to the content download request; and store said content at said first server. The computer program product may include a computer readable medium. The computer program product may include any of the features of the invention described above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention are described below, by way of example only, with reference to the following numbered Figures. 
         FIG. 1  is a block diagram of part of a known communication system; 
         FIG. 2  is a flow chart demonstrating an aspect of the use of the system of  FIG. 1 ; 
         FIG. 3  is a block diagram of part of a system in accordance with an aspect of the present invention; 
         FIG. 4  is a message sequence demonstrating an aspect of the use of the system of  FIG. 3 ; 
         FIG. 5  is a message sequence demonstrating an aspect of the use of the system of  FIG. 3  in accordance with an aspect of the present invention; 
         FIG. 6  is a message sequence demonstrating an aspect of the use of the system of  FIG. 3  in accordance with an aspect of the present invention; 
         FIG. 7  is a message sequence demonstrating an aspect of the use of the system of  FIG. 3  in accordance with an aspect of the present invention; and 
         FIG. 8  is a message sequence demonstrating an aspect of the use of the system of  FIG. 3  in accordance with an aspect of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     As discussed above, data stored in the message and media storage server  10  can be classified as either message-like contents or unstructured content (e.g. plain binary files). The two types of data may be accessed in a different manner. For example, Internet Message Access Protocol (IMAP) is one possible protocol for managing message-like contents. HTTP and Web-based Distributed Authoring and Versioning (WebDAV), which is an extension of HTTP, are two possible protocols for managing the plain binary files. 
     Since the types of the stored objects are different and the management protocols are different, it is a logical consequence to split the message and media storage server  10  into two parts. Such an arrangement is shown in  FIG. 3 . 
       FIG. 3  shows the message and media storage server  10  referred to above. The message and media storage server  10  includes a message storage server  32  and a content sharing server  34 . The message storage server  32  contains the message-like contents discussed above (including any attachments to the messages): the content sharing server  34  contains the plain binary files discussed above. In some embodiments of the invention, data stored at the message storage server  32  is accessed using the IMAP protocol and that server may be referred to as an IMAP server. Similarly, in some embodiments of the invention, data stored at the content sharing server  34  is accessed using the HTTP protocol and that server may be referred to as an HTTP server. 
       FIG. 4  shows a message sequence, indicated generally by the reference numeral  40 , showing how the algorithm  20  described above with reference to  FIG. 2  can be used to transfer data between the message storage server  32  and the content sharing server  34 . The message sequence  40  shows the data being transferred from the client  4  to the content sharing server  34  using an HTTP PUT request, with the content being included in the request body. 
     The message sequence  40  begins with the client  4  issuing an IMAP download request  42  to the message storage server  32 . In response, the message storage server  32  provides the requested content in message  44 . The client  4  then sends the content to the content sharing server  34  as an HTTP PUT request  46 . In response, the content sharing server issues an OK message  48  to the client  4 . The IMAP download request  42  and the HTTP PUT request  46  may be issued by the message and media storage client  8  of the client  4 . 
     The HTTP PUT request  46  may take the following form: 
     
       
         
               
               
               
             
           
               
                   
                   
               
             
             
               
                   
                   
                 PUT /home/ivo/MyHelloWorld.txt HTTP/1.1 
               
               
                   
                   
                 Host: myMediaStorage.operator.net 
               
               
                   
                   
                 Content-Type: text/plain 
               
               
                   
                   
                 Hello World! 
               
               
                   
                   
               
             
          
         
       
     
     Executing the HTTP PUT request  46  results in a file being created or replaced at the location given by the URL:
         http://myMediaStorage.operator.net/home/ivo/MyHelloWorld.txt       

     The content of the file created (or replaced) at that location is the text “Hello World!”. In this example, the content of the file obtained from the message storage server (the text “Hello World!”) in the message  44  is included in the HTTP PUT request  46 . It should be noted that the actual text is included in the body of the PUT request, in accordance with the normal use of the HTTP PUT request. 
     The message sequence  40  involves a first data transfer from the message storage server  32  to the client  4  and a second data transfer from the client  4  to the content sharing server  34 . This wastes network resources and incurs unnecessary costs. 
     As discussed above, in an exemplary embodiment of the invention, the message storage server  32  is an IMAP server and the content sharing server  34  is an HTTP server. Thus, in the message sequence  40 , content is obtained from the message storage server  32  using an IMAP request, and content is sent to the content sharing server  34  using an HTTP request. 
       FIGS. 5 to 8  show message sequences  50 ,  60 ,  70  and  80  respectively, in accordance with aspects of the present invention. Each of the message sequences  50 ,  60 ,  70  and  80  omits the IMAP download request  42  of the message sequence  40 . Instead, in each case, an HTTP PUT request with content reference is sent from the client  4  to the content sharing server  34 . 
     An HTTP PUT request with content reference differs from an ordinary HTTP PUT request in that, instead of the body of the request containing the actual content being transferred, the body of the request only contains a reference containing the location at which the content is stored. Further details regarding such requests can be found at http://www.ietf.org/rfc/rfc2017.txt. The HTTP PUT request with content reference is sometimes referred to in this specification as a request to copy content, since it requests that content at one server be copied to another server. 
     Each of the message sequences  50 ,  60 ,  70  and  80  makes use of the HTTP PUT request with content reference in a different way, as discussed in detail below. 
     As shown in  FIG. 5 , the message sequence  50  begins with the client  4  issuing an HTTP PUT request with content reference  52  to the content sharing server  34 . 
     In response to the request  52 , the content sharing server  34  sends an IMAP download request  54  to the message storage server  32 . The IMAP download request  54  is similar to the request  42  of the message sequence  40 , except that the request  54  is sent from the content sharing server  34  (the eventual destination of the requested content) and not the client  4 . In response to the request  54 , the message storage server  32  provides the requested content in message  56 . The message  56  is similar to the message  44 , again, with the exception of the destination of the message. 
     In response to the message  56 , the content sharing server issues an OK message  58  to the client  4 . 
     Thus, as in the message sequence  40 , the message storage server  32  receives an IMAP request and the content sharing server  34  receives an HTTP request. 
     The HTTP PUT request with content reference  52  may take the following form: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                   
                 PUT /home/ivo/MyHelloWorld.txt HTTP/1.1 
               
               
                   
                 Host: myMediaStorage.operator.net 
               
               
                   
                 Content-type: message/external-body; access-type=URL; 
               
               
                   
                 URL=“imap://MyMessageStorageServer.operator.net/ivo.sedlacek@ 
               
               
                   
                 operator.net/MyFolder/MyMail/MyAttachment” 
               
               
                   
               
             
          
         
       
     
     Executing the request  52  results in a file being created or replaced at the location given by the URL:
         http://myMediaStorage.operator.net/home/ivo/MyHelloWorld.txt
 
using the attachment stored at:
       

     
       
         
               
               
             
           
               
                   
               
             
             
               
                   
                 imap://MyMessageStorageServer.operator.net/ivo.sedlacek@operator 
               
               
                   
                 .net/MyFolder/MyMail/MyAttachment 
               
               
                   
               
             
          
         
       
     
     Upon receipt of the request  52 , the content sharing server  34  uses an integrated IMAP client to fetch the content identified by the IMAP uniform resource indicator (URI) (imap://MyMessageStorageServer.operator.net/ivo.sedlacek@operator.net/MyFolder/MyMail/MyAttachment) from the message storage server  32  and store it in the specified location of the content sharing server (steps  54  and  56  as discussed above). In order to do so, the content sharing server  34  must include an integrated IMAP client. In other words, the content sharing server needs to know how to handle IMAP URIs. 
       FIG. 6  shows a message sequence  60  in accordance with an aspect of the present invention. The message sequence  60  begins with the client  4  issuing an HTTP PUT request with content reference  62  to the content sharing server  34 . 
     In response to the request  62 , the content sharing server  34  sends an HTTP GET request  64  to the message storage server  32 . The GET request  64  initiates a download of the relevant content from the message storage server  32  and is therefore similar to the IMAP download request  54  described above with reference to  FIG. 5 . In response to the request  64 , the message storage server  32  provides the requested content in message  66 . The message  66  is similar to the message  56  described above. 
     In response to the message  66 , the content sharing server issues an OK message  68  to the client  4 . 
     The HTTP PUT request with content reference  62  may take the following form: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                   
                 PUT /home/ivo/MyHelloWorld.txt HTTP/1.1 
               
               
                   
                 Host: myMediaStorage.operator.net 
               
               
                   
                 Content-type: message/external-body;access- 
               
               
                   
                 type=URL;URL=“http://MyMessageStorageServer.operator.net:1234 
               
               
                   
                 5/CPMRedirector?TakeFrom=imap%3A%2F%2FMyMessageStorageServer. 
               
               
                   
                 operator.net%2Fivo.sedlacek@operator.net%2FMyFolder%2FMyMail% 
               
               
                   
                 2FMyAttachment” 
               
               
                   
               
             
          
         
       
     
     Executing the request  62  results in a file being created or replaced at the location given by the URL:
         http://myMediaStorage.operator.net/home/ivo/MyHelloWorld.txt
 
using the attachment stored at:
       

     
       
         
               
               
             
           
               
                   
               
             
             
               
                   
                 imap://MyMessageStorageServer.operator.net/ivo.sedlacek@operator 
               
               
                   
                 .net/MyFolder/MyMail/MyAttachment 
               
               
                   
               
             
          
         
       
     
     The HTTP GET request  64  differs from the IMAP request  54  described above in that it is an HTTP request and not an IMAP request. An IMAP request is not possible, since, in this example, it is assumed that the content sharing server  34  is not able to issue an IMAP request, for example because the content sharing server  34  does not contain an integrated IMAP client. The HTTP GET request  64  specifies the base URI of the message storage server  32  as follows: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                   
                 http://MyMessageStorageServer.operator.net:12345/CPMRedirector? 
               
               
                   
                 TakeFrom= 
               
               
                   
               
             
          
         
       
     
     The location of the requested content is provided in the TakeFrom parameter of the HTTP GET request  64  thus: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                   
                 imap://MyMessageStorageServer.operator.net/ivo.sedlacek@operator 
               
               
                   
                 .net/MyFolder/MyMail/MyAttachment 
               
               
                   
               
             
          
         
       
     
     Provided the message storage server  32  is able to understand HTTP requests, the message sequence  60  can be used, since the message storage server is able to use the TakeFrom parameter of the HTTP GET request  64  to access the content requested by the content sharing server. 
       FIG. 7  shows a message sequence  70  in accordance with an aspect of the present invention. The message sequence  70  begins with the client  4  issuing an HTTP PUT request with content reference  72  to the content sharing server  34 . In response to the request  72 , the content sharing server  34  sends an HTTP GET request  73  to a different location on the content sharing server  34 . 
     This different location hosts a resource (such as a dedicated process) on the content sharing server  34  that is able to issue IMAP requests upon receiving HTTP requests and HTTP responses upon receiving IMAP responses. 
     The HTTP GET request  73  initiates a download of the relevant content from the message storage server  32  using an IMAP download request  74 . The request  74  is largely the same as the IMAP download request  54  described above with reference to  FIG. 5 . In response to the request  74 , the message storage server  32  provides the requested content in message  76 . The message  76  is similar to the messages  56  and  66  described above (although it should be noted that the messages  56  and  76  are in response to an IMAP request, whereas the message  66  is in response to an HTTP request, and is therefore implemented differently). 
     In response to the message  76 , the content sharing server issues an OK message  77  to the originator of the request  73 . The content sharing server  34  then sends an OK message  78  to the client  4 . 
     The HTTP PUT request with content reference  72  may take the following form: 
     
       
         
               
             
           
               
                   
               
             
             
               
                 PUT /home/ivo/MyHelloWorld.txt HTTP/1.1 
               
               
                 Host: myMediaStorage.operator.net 
               
               
                 Content-type: message/external-body;access-type=URL; 
               
               
                 URL=“http://myMediaStorage.operator.net:9876/IMAPFetcher?Take 
               
               
                 From=imap%3A%2F%2FMyMessageStorageServer.operator.net%2Fivo.s 
               
               
                 edlacek@operator.net%2FMyFolder%2FMyMail%2FMyAttachment” 
               
               
                   
               
             
          
         
       
     
     The message sequence  70  differs from the message sequence  60  in that, in response to the HTTP PUT request with content reference  72 , an HTTP GET request is sent to a dedicated resource on the content sharing server, which itself sends an IMAP download request to the message storage server  32 . Thus, the message storage server  32  receives an IMAP request, without the original requesting part of the content sharing server needing to be able to issue an IMAP request. Thus, the dedicated resource of the content sharing server acts as a kind of adapter that receives an HTTP request and issues an IMAP request (and also receives an IMAP response and forwards an HTTP response). Thus, the message sequence  70  can be used in scenarios where it is not possible to issue the original request as an IMAP request and the message storage server is not able to process an HTTP request. 
     The message sequence  70  differs from the message sequence  50  in the use of the dedicated resource on the content sharing server. 
       FIG. 8  shows a message sequence  80  in accordance with an aspect of the present invention. The message sequence  80  begins with the client  4  issuing an HTTP PUT request with content reference  82  to the content sharing server  34 . 
     In response to the request  82 , the content sharing server  34  sends an HTTP GET request  84  to a third server  36 . The third server  36  may be referred to as an adapter. The third server/adapter  36  initiates a download of the relevant content from the message storage server  32  using an IMAP download request  86 . The request  86  is largely the same as the IMAP download requests  54  and  74  described above with reference to  FIGS. 5 and 7  respectively. In response to the request  86 , the message storage server  32  provides the requested content in message  88 . The message  88  is similar to the messages  56 ,  66  and  76  described above (although the messages  56 ,  76  and  88  are in response to an IMAP request, whereas the message  66  is in response to an HTTP request, and is therefore implemented differently). 
     In response to the message  88 , the third server issues an OK message  90 , together with the requested content to the content sharing server  34 . Finally, the content sharing server  34  sends an OK message (message  92 ) to the client  4 . 
     The message sequence  80  differs from the message sequence  70  in that, whereas the HTTP GET request  73  is sent from the content sharing server  34  to another location on the same server (which location is able to issue IMAP requests), the HTTP GET request  84  is sent from the content sharing server  34  to the third server  36 . Thus, the third server  36  performs the function of the dedicated resource described above. 
     The HTTP PUT request with content reference  82  may take the following form: 
     
       
         
               
             
           
               
                   
               
             
             
               
                 PUT /home/ivo/MyHelloWorld.txt HTTP/1.1 
               
               
                 Host: myMediaStorage.operator.net 
               
               
                 Content-type: message/external-body;access- 
               
               
                 type=URL;URL=“http://MyImapResolver.operator.net:12345/Resolv 
               
               
                 eImapToHttp?TakeFrom=imap%3A%2F%2FMyMessageStorageServer.oper 
               
               
                 ator.net%2Fivo.sedlacek@operator.net%2FMyFolder%2FMyMail%2FMy 
               
               
                 Attachment” 
               
               
                   
               
             
          
         
       
     
     In the message sequence  80 , the HTTP PUT request with content reference message  82  includes a base URI (providing the location of the third server) as follows: 
     http://MyImapResolver.operator.net:12345/ResolveImapToHttp?TakeFrom= 
     The provision of a base URI in the client enables the HTTP GET message  84  to be sent to the third server  36 . This arrangement is not essential. 
     The HTTP PUT request with content reference message  82  may be sent without including the base URI of the third server  36 . In such an arrangement, the content sharing server  34  may be pre-configured with the base URI of the third server  36 . (This contrasts with the embodiments described above, in which the client  4  may be pre-configured with the relevant base URI.) 
     Such an HTTP PUT request with content reference  82  may take the following form: 
     
       
         
               
               
             
           
               
                   
               
             
             
               
                   
                 PUT /home/ivo/MyHelloWorld.txt HTTP/1.1 
               
               
                   
                 Host: myMediaStorage.operator.net 
               
               
                   
                 Content-type: message/external-body; access-type=URL; 
               
               
                   
                 URL=“imap://MyMessageStorageServer.operator.net/ivo.sedlacek@ 
               
               
                   
                 operator.net/MyFolder/MyMail/MyAttachment” 
               
               
                   
               
             
          
         
       
     
     As discussed above, the content sharing server  34  is pre-configured to send the HTTP GET request  84  to the third server  36 , the URI of which is stored at the content sharing server  34 . The remainder of the message sequence  80  can proceed exactly as described above. 
     The HTTP PUT requests with content references  62  and  72  of the message sequences  60  and  70  respectively can be modified in similar ways. 
     For example, the HTTP PUT request with content reference  62  may omit the base URI of the message storage server  32 , with the content sharing server  34  being pre-configured to send the HTTP GET request  64  to the relevant resource on the message storage server  32 . Similarly, the HTTP PUT request with content reference  72  may omit the base URI of the resource on the content sharing server, with the content sharing server  34  being pre-configured to send the HTTP GET request  73  to the relevant resource on the content sharing server  34 . 
     In the various embodiments of the invention described above, the HTTP PUT requests with content reference  52 ,  62 ,  72  and  82  are described as being issued by the client  4 . Of course, in practice, those HTTP PUT requests may be issued by the message and media storage client  8  of the client  4 . 
     Many of the embodiments described above make use of the IMAP protocol to obtain data from the message storage server. This is not essential. For example, other protocols, such as FTP and gopher, could be used to obtain data instead of IMAP. 
     In the embodiments of the invention described above, the message storage server is described as being an IMAP server. This is not essential. For example, the principles of the invention can be used to copy files between two HTTP servers. 
     The content sharing server  34  is generally referred to above as an HTTP server. This is not essential. For example, the content sharing server  34  may also be a WebDAV server. 
     The embodiments of the invention described above are illustrative rather than restrictive. It will be apparent to those skilled in the art that the above devices and methods may incorporate a number of modifications without departing from the general scope of the invention. It is intended to include all such modifications within the scope of the invention insofar as they fall within the scope of the appended claims.