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+dxpc is an X protocol compressor designed to improve the
+speed of X11 applications run over low-bandwidth links
+(such as dialup PPP connections).
+
+dxpc consists of two processes:
+1. a Client Proxy that runs on the "remote" machine (the machine where
+   the X clients are running)
+2. a Server Proxy that runs on the "local" machine (the machine where
+   the X server is running)
+
+(Starting in the dxpc-3.0, release, the Client Proxy and Server Proxy
+are instances of the same program, called "dxpc"; command-line arguments
+tell the program whether it is acting as a Client Proxy or a Server Proxy.)
+
+The Client Proxy mimics an X server.  X client applications connect
+to the Client Proxy using display "unix:8" (or "<hostname>:8"; dxpc
+supports both UNIX domain and TCP sockets).  The Client Proxy receives
+X requests from the application, compresses them, and sends them to
+the Server Proxy.  The Server Proxy uncompresses the requests and
+sends them to the real X server.  Similarly, the Server Proxy receives
+X events, replies, and errors from the real X server.  It compresses
+these messages and sends them to the Client Proxy, which uncompresses
+them and sends them to the client application.
+
+dxpc attempts to exploit patterns in X protocol messages to limit
+the amount of data sent between the Client Proxy and Server Proxy.
+For many X message types, each field has a high probability of having
+the same value as it had in some previous message of the the same type.
+For such fields, dxpc maintains caches of the last 'n' values, with a
+least-recently-used replacement policy.  If a field value in a new
+message is already present in the corresponding cache, dxpc transmits
+the value's index within the cache rather than the value itself.
+Because the number of bits needed to represent this index is typically
+much smaller than the number of bits needed to represent the value
+itself, transmission of cache indices typically results in a
+significant reduction in the number of bytes transmitted over
+the low-bandwidth link.
+
+In other cases, the value of a field in an X message may differ from
+that field's value in the last message of the same type by a small
+value.  Some X messages contain sequence numbers or timestamps that
+have this property.  X requests that create new objects also tend
+to have this property; in a "Create Window" request, for example,
+the value of the "Window ID" being created is typically equal to
+"(Window ID of the last window created) + (some small positive integer)."
+For fields like these, dxpc transmits the difference between the field
+value in the new message and the value of the corresponding field in
+the previous message of the same type.  This value usually is a
+small number that can be encoded in far fewer bits than the actual
+field value.