1mX Session Management Protocol0m 1mX.Org Standard0m 1mX Version 11, Release 6.9/7.00m 4mMike24m 4mWexler0m Kubota Pacific Computer, Inc. 4mABSTRACT0m This document specifies a protocol that facili- tates the management of groups of client applica- tions by a session manager. The session manager can cause clients to save their state, to shut down, and to be restarted into a previously saved state. This protocol is layered on top of the X.Org ICE protocol. X Window System is a trademark of The Open Group. Copyright 1992, 1993, 1994, 2002 The Open Group. Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documenta- tion files (the Software), to deal in the Software with- out restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the fol- lowing conditions: The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software. THE SOFTWARE IS PROVIDED AS IS, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PUR- POSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE X CONSOR- TIUM BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE. ii 1m1. Acknowledgements0m First I would like to thank the entire ICCCM and Intrinsics working groups for the comments and suggestions. I would like to make special thanks to the following people (in alphabetical order), Jordan Brown, Ellis Cohen, Donna Con- verse, Vania Joloboff, Stuart Marks, Ralph Mor and Bob Scheifler. 1m2. Definitions and Goals0m The purpose of the X Session Management Protocol (XSMP) is to provide a uniform mechanism for users to save and restore their sessions. A 4msession24m is a group of clients, each of which has a particular state. The session is controlled by a network service called the 4msession24m 4mmanager24m. The session manager issues commands to its clients on behalf of the user. These commands may cause clients to save their state or to terminate. It is expected that the client will save its state in such a way that the client can be restarted at a later time and resume its operation as if it had never been terminated. A clients state might include information about the file currently being edited, the current position of the insertion point within the file, or the start of an uncommitted transaction. The means by which clients are restarted is unspecified by this protocol. For purposes of this protocol, a 4mclient24m of the session man- ager is defined as a connection to the session manager. A client is typically, though not necessarily, a process run- ning an application program connected to an X Window System display. However, a client may be connected to more than one X display or not be connected to any X displays at all. This protocol is layered on top of the X Consortiums ICE protocol and relies on the ICE protocol to handle connection management and authentication. 1m3. Overview of the Protocol0m Clients use XSMP to register themselves with the session manager (SM). When a client starts up, it should connect to the SM. The client should remain connected for as long as it runs. A client may resign from the session by issuing the proper protocol messages before disconnecting. Termina- tion of the connection without notice will be taken as an indication that the client died unexpectedly. Clients are expected to save their state in such a way as to allow multiple instantiations of themselves to be managed independently. A unique value called a 4mclient-ID24m is pro- vided by the protocol for the purpose of disambiguating mul- tiple instantiations of clients. Clients may use this ID, 1m10m 1mX Session Management Protocol X11, Release 6.9/7.00m for example, as part of a filename in which to store the state for a particular instantiation. The client-ID should be saved as part of the command used to restart this client (the 4mRestartCommand24m) so that the client will retain the same ID after it is restarted. Certain small pieces of state might also be stored in the RestartCommand. For example, an X11 client might place a twoWindow option in its RestartCommand to indicate that it should start up in two window mode when it is restarted. The client finds the network address of the SM in a system- dependent way. On POSIX systems an environment variable called SESSION_MANAGER will contain a list of network IDs. Each id will contain the transport name followed by a slash and the (transport-specific) address. A TCP/IP address would look like this: tcp/4mhostname24m:4mportnumber0m where the hostname is a fully qualified domain name. A Unix Domain address looks like this: local/4mhostname24m:4mpath0m A DECnet address would look like this: decnet/4mnodename24m::4mobjname0m If multiple network IDs are specified, they should be sepa- rated by commas. Rationale There was much discussion over whether the XSMP protocol should use X as the transport protocol or whether it should use its own independent trans- port. It was decided that it would use an inde- pendent protocol for several reasons. First, the Session Manager should be able to manage programs that do not maintain an X connection. Second, the X protocol is not appropriate to use as a general- purpose transport protocol. Third, a session might span multiple displays. The protocol is connection based, because there is no other way for the SM to determine reliably when clients terminate. It should be noted that this protocol introduces another single point of failure into the system. Although it is possible for clients to continue running after the SM has exited, this will proba- bly not be the case in normal practice. Normally the program that starts the SM will consider the 1m20m 1mX Session Management Protocol X11, Release 6.9/7.00m session to be terminated when the SM exits (either normally or abnormally). To get around this would require some sort of ren- dezvous server that would also introduce a single point of failure. In the absence of a generally available rendezvous server, XSMP is kept simple in the hopes of making simple reliable SMs. Some clients may wish to manage the programs they start. For example, a mail program could start a text editor for editing the text of a mail message. A client that does this is a session manager itself; it should supply the clients it starts with the appropriate connection information (i.e., the SESSION_MANAGER environment variable) that specifies a connection to itself instead of to the top level session manager. Each client has associated with it a list of properties. A property set by one client is not visible to any other client. These properties are used for the client to inform the SM of the clients current state. When a client ini- tially connects to the SM, there are no properties set. 1m4. Data Types0m XSMP messages contain several types of data. Both the SM and the client always send messages in their native byte order. Thus, both sides may need to byte-swap the messages received. The need to do byte-swapping is determined at run-time by the ICE protocol. If an invalid value is specified for a field of any of the enumerated types, a 4mBadValue24m error message must be sent by the receiver of the message to the sender of the message. ------------------------------------------------------------------------------------ 1mType Name Description0m ------------------------------------------------------------------------------------ BOOL 4mFalse24m or 4mTrue0m INTERACT_STYLE 4mNone24m, 4mErrors24m, or 4mAny0m DIALOG_TYPE 4mError24m or 4mNormal0m SAVE_TYPE 4mGlobal24m, 4mLocal24m, or 4mBoth0m CARD8 a one-byte unsigned integer CARD16 a two-byte unsigned integer CARD32 a four-byte unsigned integer ARRAY8 a sequence of CARD8s LISTofARRAY8 a sequence of ARRAY8s PROPERTY a property name (an ARRAY8), a type name, and a value of that type LISTofPROPERTY a counted collection of PROPERTYs. ------------------------------------------------------------------------------------ 1m30m 1mX Session Management Protocol X11, Release 6.9/7.00m 1m5. Protocol Setup and Message Format0m To start the XSMP protocol, the client sends the server an ICE 4mProtocolSetup24m message. All XSMP messages are in the standard ICE message format. The messages major opcode is assigned to XSMP by ICE at run-time. The different parties (client and SM) may be assigned different major opcodes for XSMP. Once assigned, all XSMP messages issued by this party will use the same major opcode. The messages minor opcode specifies which protocol message this message contains. 1m6. Client Identification String0m A client ID is a string of XPCS characters encoded in ISO Latin 1 (ISO 8859-1). No null characters are allowed in this string. The client ID string is used in the 4mRegister-0m 4mClient24m and 4mRegisterClientReply24m messages. Client IDs consist of the pieces described below. The ID is formed by concatenating the pieces in sequence, without sep- arator characters. All pieces are padded on the left with 0 characters so as to fill the specified length. Decimal numbers are encoded using the characters 0 through 9, and hexadecimal numbers using the characters 0 through 9 and A through F. Version. This is currently the character 1. Address type and address. The address type will be one of 1 a 4-byte IPv4 address encoded as 8 hexadecimal digits 2 a 6-byte DECNET address encoded as 12 hexadecimal digits 6 a 16-byte IPv6 address encoded as 32 hexadecimal digits The address is the one of the network addresses of the machine where the session manager (not the client) is running. For example, the IP address 198.112.45.11 would be encoded as the string "C6702D0B". Time stamp. A 13-digit decimal number specifying the number of milliseconds since 00:00:00 UTC, January 1, 1970. Process-ID type and process-ID. The process-ID type will be one of 1 a POSIX process-ID encoded as a 10-digit decimal number. The process-ID is the process-ID of the session manager, not of a client. 1m40m 1mX Session Management Protocol X11, Release 6.9/7.00m Sequence number. This is a four-digit decimal number. It is incremented every time the session manager creates an ID. After reaching "9999" it wraps to "0000". Rationale Once a client ID has been assigned to the client, the client keeps this ID indefinitely. If the client is terminated and restarted, it will be reassigned the same ID. It is desir- able to be able to pass client IDs around from machine to machine, from user to user, and from session manager to session manager, while retaining the identity of the client. This, combined with the indefinite persistence of client IDs, means that client IDs need to be globally unique. The construction specified above will ensure that any client ID created by any user, session manager, and machine will be different from any other. 1m7. Protocol0m The protocol consists of a sequence of messages as described below. Each message type is specified by an ICE minor opcode. A given message type is sent either from a client to the session manager or from the session manager to a client; the appropriate direction is listed with each mes- sages description. For each message type, the set of valid responses and possible error messages are listed. The ICE severity is given in parentheses following each error class. __ 4mRegisterClient24m [Client SM] 4mprevious-ID24m: ARRAY8 Valid Responses: 4mRegisterClientReply0m __ Possible Errors: 4mBadValue24m (4mCanContinue24m) The client must send this message to the SM to register the clients existence. If a client is being restarted from a previous session, the previous-ID field must contain the client ID from the previous session. For new clients, pre- vious-ID should be of zero length. If previous-ID is not valid, the SM will send a 4mBadValue0m error message to the client. At this point the SM reverts to the register state and waits for another 4mRegisterClient24m. The client should then send a 4mRegisterClient24m with a null previous-ID field. 1m50m 1mX Session Management Protocol X11, Release 6.9/7.00m __ 4mRegisterClientReply24m [Client SM] __ 4mclient-ID24m: ARRAY8 The client-ID specifies a unique identification for this client. If the client had specified an ID in the previous- ID field of the 4mRegisterClient24m message, client-ID will be identical to the previously specified ID. If previous-ID was null, client-ID will be a unique ID freshly generated by the SM. The client-ID format is specified in section 6. If the client didnt supply a previous-ID field to the 4mRegisterClient24m message, the SM must send a 4mSaveYourself24m mes- sage with type = Local, shutdown = False, interact-style = None, and fast = False immediately after the 4mRegisterClien-0m 4mtReply24m. The client should respond to this like any other 4mSaveYourself24m message. __ 4mSaveYourself24m [Client SM] 4mtype24m: SAVE_TYPE 4mshutdown24m: BOOL 4minteract-style24m: INTERACT_STYLE 4mfast24m: BOOL Valid Responses: 4mSetProperties24m, 4mDeleteProperties24m, 4mGet-0m 4mProperties24m, 4mSaveYourselfDone24m, 4mSaveYourself-0m __ 4mPhase2Request24m, 4mInteractRequest0m The SM sends this message to a client to ask it to save its state. The client writes a state file, if necessary, and, if necessary, uses 4mSetProperties24m to inform the SM of how to restart it and how to discard the saved state. During this process it can, if allowed by interact-style, request per- mission to interact with the user by sending an 4mInteractRe-0m 4mquest24m message. After the state has been saved, or if it cannot be successfully saved, and the properties are appro- priately set, the client sends a 4mSaveYourselfDone24m message. If the client wants to save additional information after all the other clients have finished changing their own state, the client should send 4mSaveYourselfPhase2Request24m instead of 4mSaveYourselfDone24m. The client must then freeze interaction with the user and wait until it receives a 4mSaveComplete24m, 4mDie24m, or a 4mShutdownCancelled24m message. If interact-style is 4mNone24m, the client must not interact with the user while saving state. If the interact-style is 4mErrors24m, the client may interact with the user only if an error condition arises. If interact-style is 4mAny24m, then the client may interact with the user for any purpose. This is done by sending an 4mInteractRequest24m message. The SM will 1m60m 1mX Session Management Protocol X11, Release 6.9/7.00m send an 4mInteract24m message to each client that sent an 4mInteractRequest24m. The client must postpone all interaction until it gets the 4mInteract24m message. When the client is done interacting it should send the SM an 4mInteractDone24m message. The 4mInteractRequest24m message can be sent any time after a 4mSaveYourself24m and before a 4mSaveYourselfDone24m. Unusual circumstances may dictate multiple interactions. The client may initiate as many 4mInteractRequest24m 4mInteract24m 4mInteractDone24m sequences as it needs before it sends 4mSaveYour-0m 4mselfDone24m. When a client receives 4mSaveYourself24m and has not yet responded 4mSaveYourselfDone24m to a previous 4mSaveYourself24m, it must send a 4mSaveYourselfDone24m and may then begin responding as appropriate to the newly received 4mSaveYourself24m. The type field specifies the type of information that should be saved: 4mGlobal24m, 4mLocal24m, or 4mBoth24m. The 4mLocal24m type indicates that the application must update the properties to reflect its current state, send a 4mSaveYourselfDone24m and continue. Specifically it should save enough information to restore the state as seen by the user of this client. It should not affect the state as seen by other users. The 4mGlobal24m type indicates that the user wants the client to commit all of its data to permanent, globally-accessible storage. 4mBoth0m indicates that the client should do both of these. If 4mBoth0m is specified, the client should first commit the data to permanent storage before updating its SM properties. Examples If a word processor was sent a 4mSaveYourself24m with a type of 4mLocal24m, it could create a temporary file that included the current contents of the file, the location of the cursor, and other aspects of the current editing session. It would then update its 4mRestartCommand24m property with enough informa- tion to find the temporary file, and its 4mDiscard-0m 4mCommand24m with enough information to remove it. If a word processor was sent a 4mSaveYourself24m with a type of 4mGlobal24m, it would simply save the currently edited file. If a word processor was sent a 4mSaveYourself24m with a type of 4mBoth24m, it would first save the currently edited file. It would then create a temporary file with information such as the current position of the cursor and what file is being edited. It would then update its 4mRestartCommand24m property with enough information to find the temporary file, and its 4mDiscardCommand24m with enough information to remove it. 1m70m 1mX Session Management Protocol X11, Release 6.9/7.00m Once the SM has send 4mSaveYourself24m to a client, it cant send another 4mSaveYourself24m to that client until the client either responds with a 4mSaveYour-0m 4mselfDone24m or the SM sends a 4mShutdownCancelled24m. Advice to Implementors If the client stores local any state in a file or similar "external" storage, it must create a dis- tinct copy in response to each 4mSaveYourself24m mes- sage. It 4mmust24m 4mnot24m simply refer to a previous copy, because the SM may discard that previous saved state using a 4mDiscardCommand24m without knowing that it is needed for the new checkpoint. The shutdown field specifies whether the system is being shut down. Rationale The interaction may be different depending on whether or not shutdown is set. The client must save and then must prevent interaction until it receives a 4mSaveComplete24m, 4mDie24m, or a 4mShutdownCancelled24m, because anything the user does after the save will be lost. The fast field specifies whether or not the client should save its state as quickly as possible. For example, if the SM knows that power is about to fail, it should set the fast field to 4mTrue24m. __ 4mSaveYourselfPhase224m [Client SM] Valid Responses: 4mSetProperties24m, 4mDeleteProperties24m, 4mGet-0m __ 4mProperties24m, 4mSaveYourselfDone24m, 4mInteractRequest0m The SM sends this message to a client that has previously sent a 4mSaveYourselfPhase2Request24m message. This message informs the client that all other clients are in a fixed state and this client can save state that is associated with other clients. Rationale Clients that manager other clients (window man- agers, workspace managers, etc) need to know when all clients they are managing are idle, so that the manager can save state related to each of the 1m80m 1mX Session Management Protocol X11, Release 6.9/7.00m clients without being concerned with that state changing. The client writes a state file, if necessary, and, if neces- sary, uses 4mSetProperties24m to inform the SM of how to restart it and how to discard the saved state. During this process it can request permission to interact with the user by send- ing an 4mInteractRequest24m message. This should only be done if an error occurs that requires user interaction to resolve. After the state has been saved, or if it cannot be success- fully saved, and the properties are appropriately set, the client sends a 4mSaveYourselfDone24m message. __ 4mSaveYourselfRequest24m [Client SM] 4mtype24m: SAVE_TYPE 4mshutdown24m: BOOL 4minteract-style24m: INTERACT_STYLE 4mfast24m: BOOL 4mglobal24m: BOOL __ Valid Responses: 4mSaveYourself0m An application sends this to the SM to request a checkpoint. When the SM receives this request it may generate a 4mSaveY-0m 4mourself24m message in response and it may leave the fields intact. Example A vendor of a UPS (Uninterruptible Power Supply) might include an SM client that would monitor the status of the UPS and generate a fast shutdown if the power is about to be lost. If global is set to 4mTrue24m, then the resulting 4mSaveYourself0m should be sent to all applications. If global is set to 4mFalse24m, then the resulting 4mSaveYourself24m should be sent to the application that sent the 4mSaveYourselfRequest24m. __ 4mInteractRequest24m [Client SM] 4mdialog-type24m: DIALOG_TYPE Valid Responses: 4mInteract24m, 4mShutdownCancelled0m __ Possible Errors: 4mBadState24m (4mCanContinue24m) 1m90m 1mX Session Management Protocol X11, Release 6.9/7.00m During a checkpoint or session-save operation, only one client at a time might be granted the privilege of interact- ing with the user. The 4mInteractRequest24m message causes the SM to emit an 4mInteract24m message at some later time if the shutdown is not cancelled by another client first. The dialog-type field specifies either 4mErrors24m, indicating that the client wants to start an error dialog or 4mNormal24m, meaning the client wishes to start a non-error dialog. __ 4mInteract24m [Client SM] Valid Responses: 4mInteractDone0m __ This message grants the client the privilege of interacting with the user. When the client is done interacting with the user it must send an 4mInteractDone24m message to the SM unless a shutdown cancel is received. Advice to Implementors If a client receives a ShutdownCancelled after receiving an 4mInteract24m message, but before sending a 4mInteractDone24m, the client should abort the inter- action and send a 4mSaveYourselfDone24m. __ 4mInteractDone24m [Client SM] 4mcancel-shutdown24m: BOOL Valid Responses: 4mShutdownCancelled0m __ This message is used by a client to notify the SM that it is done interacting. Setting the cancel-shutdown field to 4mTrue24m indicates that the user has requested that the entire shutdown be cancelled. Cancel-shutdown may only be 4mTrue24m if the corresponding 4mSaveY-0m 4mourself24m message specified 4mTrue24m for the shutdown field and 4mAny24m or 4mErrors24m for the interact-style field. Otherwise, can- cel-shutdown must be 4mFalse24m. 1m100m 1mX Session Management Protocol X11, Release 6.9/7.00m __ 4mSaveYourselfDone24m [Client SM] 4msuccess24m: BOOL Valid Responses: 4mSaveComplete24m, 4mDie24m, 4mShutdownCancelled0m __ This message is sent by a client to indicate that all of the properties representing its state have been updated. After sending 4mSaveYourselfDone24m the client must wait for a 4mSaveCom-0m 4mplete24m, 4mShutdownCancelled24m, or 4mDie24m message before changing its state. If the 4mSaveYourself24m operation was successful, then the client should set the success field to 4mTrue24m; otherwise the client should set it to 4mFalse24m. Example If a client tries to save its state and runs out of disk space, it should return 4mFalse24m in the suc- cess field of the 4mSaveYourselfDone24m message. __ 4mSaveYourselfPhase2Request24m [Client SM] Valid Responses: 4mShutdownCancelled24m, 4mSaveYourselfPhase20m __ This message is sent by a client to indicate that it needs to be informed when all the other clients are quiescent, so it can continue its state. __ 4mDie24m [Client SM] __ Valid Responses: 4mConnectionClosed0m When the SM wants a client to die it sends a 4mDie24m message. Before the client dies it responds by sending a 4mConnection-0m 4mClosed24m message and may then close its connection to the SM at any time. __ 4mSaveComplete24m [Client SM] __ Valid Responses: When the SM is done with a checkpoint, it will send each of the clients a 4mSaveComplete24m message. The client is then free to change its state. 1m110m 1mX Session Management Protocol X11, Release 6.9/7.00m __ __ 4mShutdownCancelled24m [Client SM] The shutdown currently in process has been aborted. The client can now continue as if the shutdown had never hap- pened. If the client has not sent 4mSaveYourselfDone24m yet, the client can either abort the save and send 4mSaveYourselfDone0m with the success field set to 4mFalse24m, or it can continue with the save and send a 4mSaveYourselfDone24m with the success field set to reflect the outcome of the save. __ 4mConnectionClosed24m [Client SM] __ 4mreason24m: LISTofARRAY8 Specifies that the client has decided to terminate. It should be immediately followed by closing the connection. The reason field specifies why the client is resigning from the session. It is encoded as an array of Compound Text strings. If the resignation is expected by the user, there will typically be zero ARRAY8s here. But if the client encountered an unexpected fatal error, the error message (which might otherwise be printed on stderr on a POSIX sys- tem) should be forwarded to the SM here, one ARRAY8 per line of the message. It is the responsibility of the SM to dis- play this reason to the user. After sending this message, the client must not send any additional XSMP messages to the SM. Advice to Implementors If additional messages are received, they should be discarded. Rationale The reason for sending the 4mConnectionClosed24m mes- sage before actually closing the connections is that some transport protocols will not provide immediate notification of connection closure. __ 4mSetProperties24m [Client SM] __ 4mproperties24m: LISTofPROPERTY 1m120m 1mX Session Management Protocol X11, Release 6.9/7.00m Sets the specified properties to the specified values. Existing properties not specified in the 4mSetProperties24m mes- sage are unaffected. Some properties have predefined seman- tics. See section 11, "Predefined Properties." The protocol specification recommends that property names used for properties not defined by the standard should begin with an underscore. To prevent conflicts among organiza- tions, additional prefixes should be chosen (for example, _KPC_FAST_SAVE_OPTION). The organizational prefixes should be registered with the X Registry. The XSMP reserves all property names not beginning with an underscore for future use. __ 4mDeleteProperties24m [Client SM] __ 4mproperty-names24m: LISTofARRAY8 Removes the named properties. __ 4mGetProperties24m [Client SM] __ Valid Responses: 4mGetPropertiesReply0m Requests that the SM respond with the values of all the properties for this client. __ 4mGetPropertiesReply24m [Client SM] __ 4mvalues24m: LISTofPROPERTY This message is sent in reply to a 4mGetProperties24m message and includes the values of all the properties. 1m8. Errors0m When the receiver of a message detects an error condition, the receiver sends an ICE error message to the sender. There are only two types of errors that are used by the XSMP: 4mBadValue24m and 4mBadState24m. These are both defined in the ICE protocol. Any message received out-of-sequence will generate a 4mBad-0m 4mState24m error message. 1m130m 1mX Session Management Protocol X11, Release 6.9/7.00m 1m9. State Diagrams0m These state diagrams are designed to cover all actions of both the client and the SM. 1m9.1. Client State Diagram0m 4mstart:0m ICE protocol setup complete register 4mregister:0m send 1mRegisterClient 22m collect-id 4mcollect-id:0m receive 1mRegisterClientReply 22m idle 4mshutdown-cancelled:0m send 1mSaveYourselfDone 22m idle 4midle:24m [Undoes any freeze of interaction with user.] receive 1mDie 22m die receive 1mSaveYourself 22m freeze-interaction send 1mGetProperties 22m idle receive 1mGetPropertiesReply 22m idle send 1mSetProperties 22m idle send 1mDeleteProperties 22m idle send 1mConnectionClosed 22m connection-closed send 1mSaveYourselfRequest 22m idle 4mdie:0m send 1mConnectionClosed 22m connection-closed 4mfreeze-interaction:0m freeze interaction with user save-yourself 1m140m 1mX Session Management Protocol X11, Release 6.9/7.00m 4msave-yourself:0m receive 1mShutdownCancelled 22m shutdown-cancelled send 1mSetProperties 22m save-yourself send 1mDeleteProperties 22m save-yourself send 1mGetProperties 22m save-yourself receive 1mGetPropertiesReply 22m save-yourself send 1mInteractRequest 22m interact-request send 1mSaveYourselfPhase2Request 22m-> waiting-for-phase2 if shutdown mode: send 1mSaveYourselfDone 22m save-yourself-done otherwise: send 1mSaveYourselfDone 22m idle 4mwaiting-for-phase2:0m receive 1mShutdownCancelled 22m shutdown-cancelled receive 1mSaveYourselfPhase2 22m phase2 4mphase2:0m receive 1mShutdownCancelled 22m shutdown-cancelled send 1mSetProperties 22m save-yourself send 1mDeleteProperties 22m save-yourself send 1mGetProperties 22m save-yourself receive 1mGetPropertiesReply 22m save-yourself send 1mInteractRequest 22m interact-request (errors only) if shutdown mode: send 1mSaveYourselfDone 22m save-yourself-done otherwise: send 1mSaveYourselfDone 22m idle 4minteract-request:0m receive 1mInteract 22m interact receive 1mShutdownCancelled 22m shutdown-cancelled 4minteract:0m send 1mInteractDone 22m save-yourself receive 1mShutdownCancelled 22m shutdown-cancelled 4msave-yourself-done:24m (changing state is forbidden) receive 1mSaveComplete 22m idle receive 1mDie 22m die receive 1mShutdownCancelled 22m idle 1m150m 1mX Session Management Protocol X11, Release 6.9/7.00m 4mconnection-closed:0m client stops participating in session 1m9.2. Session Manager State Diagram0m 4mstart:0m receive 1mProtocolSetup 22m protocol-setup 4mprotocol-setup:0m send 1mProtocolSetupReply 22m register 4mregister:0m receive 1mRegisterClient 22m acknowledge-register 4macknowledge-register:0m send 1mRegisterClientReply 22m idle 4midle:0m receive 1mSetProperties 22m idle receive 1mDeleteProperties 22m idle receive 1mConnectionClosed 22m start receive 1mGetProperties 22m get-properties receive 1mSaveYourselfRequest 22m save-yourself send 1mSaveYourself 22m saving-yourself 4msave-yourself:0m send 1mSaveYourself 22m saving-yourself 4mget-properties:0m send 1mGetPropertiesReply 22m idle 4msaving-get-properties:0m send 1mGetPropertiesReply 22m saving-yourself 1m160m 1mX Session Management Protocol X11, Release 6.9/7.00m 4msaving-yourself:0m receive 1mInteractRequest 22m saving-yourself send 1mInteract 22m saving-yourself send 1mShutdownCancelled 22m-> idle receive 1mInteractDone 22m saving-yourself receive 1mSetProperties 22m saving-yourself receive 1mDeleteProperties 22m saving-yourself receive 1mGetProperties 22m saving-get-properties receive 1mSaveYourselfPhase2Request 22m start-phase2 receive 1mSaveYourselfDone 22m save-yourself-done 4mstart-phase2:0m If all clients have sent either 1mSaveYourselfPhase2Request 22mor 1mSaveYourselfDone22m: send 1mSaveYourselfPhase2 22m phase2 else saving-yourself 4mphase2:0m receive 1mInteractRequest 22m saving-yourself send 1mInteract 22m saving-yourself send 1mShutdownCancelled 22m-> idle receive 1mInteractDone 22m saving-yourself receive 1mSetProperties 22m saving-yourself receive 1mDeleteProperties 22m saving-yourself receive 1mGetProperties 22m saving-get-properties receive 1mSaveYourselfDone 22m save-yourself-done 4msave-yourself-done:0m If all clients are saved: If shutting down: send 1mDie 22m die otherwise send 1mSaveComplete 22m idle If some clients are not saved: saving-yourself 4mdie:0m SM stops accepting connections 1m10. Protocol Encoding0m 1m170m 1mX Session Management Protocol X11, Release 6.9/7.00m 1m10.1. Types0m BOOL 0 False 1 True INTERACT_STYLE 0 None 1 Errors 2 Any DIALOG_TYPE 0 Error 1 Normal SAVE_TYPE 0 Global 1 Local 2 Both ARRAY8 4 CARD32 length n LISTofCARD8 the array p p = pad (4 + n, 8) LISTofARRAY8 4 CARD32 count 4 unused a ARRAY8 first array b ARRAY8 second array . . . q ARRAY8 last array PROPERTY a ARRAY8 name b ARRAY8 type (XPCS encoded in Latin-1, case sensitive) c LISTofARRAY8 values LISTofPROPERTY 4 CARD32 count 4 unused a PROPERTY first property b PROPERTY second property . . . q PROPERTY last property 1m10.2. Messages0m XSMP is a sub-protocol of ICE. The major opcode is assigned at run-time by ICE and is represented here by ?. 1m180m 1mX Session Management Protocol X11, Release 6.9/7.00m To start the XSMP protocol, the client sends the server an ICE 4mProtocolSetup24m message. The protocol-name field should be specified as "XSMP", the major version of the protocol is 1, the minor version is 0. These values may change if the protocol is revised. The minor version number will be incremented if the change is compatible, otherwise the major version number will be incremented. In 4mProtocolReply24m message sent by the session manager, the XSMP protocol defines the vendor parameter as product iden- tification of the session manager, and defines the release parameter as the software release identification of the ses- sion manager. The session manager should supply this infor- mation in the ICE 4mProtocolReply24m message. 4mRegisterClient0m 1 ? XSMP 1 1 opcode 2 unused 4 a/8 length of remaining data in 8-byte units a ARRAY8 previous-ID 4mRegisterClientReply0m 1 ? XSMP 1 2 opcode 2 unused 4 a/8 length of remaining data in 8-byte units a ARRAY8 client-ID 4mSaveYourself0m 1 ? XSMP 1 3 opcode 2 unused 4 1 length of remaining data in 8-byte units 1 SAVE_TYPE type 1 BOOL shutdown 1 INTERACT_STYLE interact-style 1 BOOL fast 4 unused 4mSaveYourselfRequest0m 1 ? XSMP 1 4 opcode 2 unused 4 1 length of remaining data in 8-byte units 1 SAVE_TYPE type 1 BOOL shutdown 1 INTERACT_STYLE interact-style 1 BOOL fast 1 BOOL global 3 unused 1m190m 1mX Session Management Protocol X11, Release 6.9/7.00m 4mInteractRequest0m 1 ? XSMP 1 5 opcode 1 DIALOG_TYPE dialog type 1 unused 4 0 length of remaining data in 8-byte units 4mInteract0m 1 ? XSMP 1 6 opcode 2 unused 4 0 length of remaining data in 8-byte units 4mInteractDone0m 1 ? XSMP 1 7 opcode 1 BOOL cancel-shutdown 1 unused 4 0 length of remaining data in 8-byte units 4mSaveYourselfDone0m 1 ? XSMP 1 8 opcode 1 BOOL success 1 unused 4 0 length of remaining data in 8-byte units 4mDie0m 1 ? XSMP 1 9 opcode 2 unused 4 0 length of remaining data in 8-byte units 4mShutdownCancelled0m 1 ? XSMP 1 10 opcode 2 unused 4 0 length of remaining data in 8-byte units 4mConnectionClosed0m 1 ? XSMP 1 11 opcode 2 unused 4 a/8 length of remaining data in 8-byte units a LISTofARRAY8 reason 4mSetProperties0m 1 ? XSMP 1 12 opcode 2 unused 4 a/8 length of remaining data in 8-byte units a LISTofPROPERTY properties 1m200m 1mX Session Management Protocol X11, Release 6.9/7.00m 4mDeleteProperties0m 1 ? XSMP 1 13 opcode 2 unused 4 a/8 length of remaining data in 8-byte units a LISTofARRAY8 properties 4mGetProperties0m 1 ? XSMP 1 14 opcode 2 unused 4 0 length of remaining data in 8-byte units 4mGetPropertiesReply0m 1 ? XSMP 1 15 opcode 2 unused 4 a/8 length of remaining data in 8-byte units a LISTofPROPERTY properties 4mSaveYourselfPhase2Request0m 1 ? XSMP 1 16 opcode 2 unused 4 0 length of remaining data in 8-byte units 4mSaveYourselfPhase20m 1 ? XSMP 1 17 opcode 2 unused 4 0 length of remaining data in 8-byte units 4mSaveComplete0m 1 ? XSMP 1 18 opcode 2 unused 4 0 length of remaining data in 8-byte units 1m11. Predefined Properties0m All property values are stored in a LISTofARRAY8. If the type of the property is CARD8, the value is stored as a LISTofARRAY8 with one ARRAY8 that is one byte long. That single byte contains the CARD8. If the type of the property is ARRAY8, the value is stored in the first element of a single element LISTofARRAY8. The required properties must be set each time a client con- nects with the SM. The properties must be set after the client sends 4mRegisterClient24m and before the client sends 4mSaveYourselfDone24m. Otherwise, the behavior of the session manager is not defined. 1m210m 1mX Session Management Protocol X11, Release 6.9/7.00m Clients may set, get, and delete nonstandard properties. The lifetime of stored properties does not extend into sub- sequent sessions. ---------------------------------------------------------- 1mName Type Posix Type Required?0m ---------------------------------------------------------- CloneCommand OS-specific LISTofARRAY8 Yes CurrentDirectory OS-specific ARRAY8 No DiscardCommand OS-specific LISTofARRAY8 No* Environment OS-specific LISTofARRAY8 No ProcessID OS-specific ARRAY8 No Program OS-specific ARRAY8 Yes RestartCommand OS-specific LISTofARRAY8 Yes ResignCommand OS-specific LISTofARRAY8 No RestartStyleHint CARD8 CARD8 No ShutdownCommand OS-specific LISTofARRAY8 No UserID ARRAY8 ARRAY8 Yes ---------------------------------------------------------- * Required if any state is stored in an external repository (e.g., state file). CloneCommand This is like the 4mRestartCommand24m except it restarts a copy of the application. The only difference is that the application doesnt supply its client id at register time. On POSIX systems the type should be a LISTofAR- RAY8. CurrentDirectory On POSIX-based systems specifies the value of the current directory that needs to be set up prior to starting the program and should be of type ARRAY8. DiscardCommand The discard command contains a command that when deliv- ered to the host that the client is running on (deter- mined from the connection), will cause it to discard any information about the current state. If this command is not specified, the SM will assume that all of the clients state is encoded in the 4mRestartCommand24m. On POSIX systems the type should be LISTofARRAY8. Environment On POSIX based systems, this will be of type LISTofARRAY8 where the ARRAY8s alternate between environment variable name and environment variable value. ProcessID This specifies an OS-specific identifier for the process. On POSIX systems this should of type ARRAY8 and contain the return value of getpid() turned into a Latin-1 1m220m 1mX Session Management Protocol X11, Release 6.9/7.00m (decimal) string. Program The name of the program that is running. On POSIX sys- tems this should be the first parameter passed to execve and should be of type ARRAY8. RestartCommand The restart command contains a command that when deliv- ered to the host that the client is running on (deter- mined from the connection), will cause the client to restart in its current state. On POSIX-based systems this is of type LISTofARRAY8 and each of the elements in the array represents an element in the argv array. This restart command should ensure that the client restarts with the specified client-ID. ResignCommand A client that sets the 4mRestartStyleHint24m to 4mRestartAnyway0m uses this property to specify a command that undoes the effect of the client and removes any saved state. Example A user runs xmodmap. xmodmap registers with the SM, sets 4mRestartStyleHint24m to 4mRestartAnyway24m, and then terminates. In order to allow the SM (at the users request) to undo this, xmodmap would register a 4mResignCommand24m that undoes the effects of the xmodmap. RestartStyleHint If the RestartStyleHint property is present, it will con- tain the style of restarting the client prefers. If this flag isnt specified, 4mRestartIfRunning24m is assumed. The possible values are as follows: --------------------------- 1mName Value0m --------------------------- RestartIfRunning 0 RestartAnyway 1 RestartImmediately 2 RestartNever 3 --------------------------- The 4mRestartIfRunning24m style is used in the usual case. The client should be restarted in the next session if it is connected to the session manager at the end of the current session. 1m230m 1mX Session Management Protocol X11, Release 6.9/7.00m The 4mRestartAnyway24m style is used to tell the SM that the application should be restarted in the next session even if it exits before the current session is terminated. It should be noted that this is only a hint and the SM will follow the policies specified by its users in determining what applications to restart. Rationale This can be specified by a client which sup- ports (as MS-Windows clients do) a means for the user to indicate while exiting that restarting is desired. It can also be used for clients that spawn other clients and then go away, but which want to be restarted. A client that uses 4mRestartAnyway24m should also set the 4mResignCommand24m and 4mShutdownCommand24m properties to commands that undo the state of the client after it exits. The 4mRestartImmediately24m style is like 4mRestartAnyway24m, but in addition, the client is meant to run continuously. If the client exits, the SM should try to restart it in the current session. Advice to Implementors It would be wise to sanity-check the frequency which which 4mRestartImmediately24m clients are restarted, to avoid a sick client being restarted continuously. The 4mRestartNever24m style specifies that the client does not wish to be restarted in the next session. Advice To Implementors This should be used rarely, if at all. It will cause the client to be silently left out of sessions when they are restarted and will prob- ably be confusing to users. ShutdownCommand This command is executed at shutdown time to clean up after a client that is no longer running but retained its state by setting 4mRestartStyleHint24m to 4mRestartAnyway24m. The command must not remove any saved state as the client is still part of the session. 1m240m 1mX Session Management Protocol X11, Release 6.9/7.00m Example A client is run at start up time that turns on a camera. This client then exits. At session shutdown, the user wants the camera turned off. This client would set the 4mRestartStyleHint24m to 4mRestartAnyway24m and would register a 4mShutdown-0m 4mCommand24m that would turn off the camera. UserID Specifies the users ID. On POSIX-based systems this will contain the the users name (the pw_name field of struct passwd). 1m250m 1mX Session Management Protocol X11, Release 6.9/7.00m 1m260m 1mX Session Management Protocol X11, Release 6.9/7.00m 1mTable of Contents0m 1. Acknowledgements . . . . . . . . . . . . . . . . . 1 2. Definitions and Goals . . . . . . . . . . . . . . 1 3. Overview of the Protocol . . . . . . . . . . . . . 1 4. Data Types . . . . . . . . . . . . . . . . . . . . 3 5. Protocol Setup and Message Format . . . . . . . . 4 6. Client Identification String . . . . . . . . . . . 4 7. Protocol . . . . . . . . . . . . . . . . . . . . . 5 8. Errors . . . . . . . . . . . . . . . . . . . . . . 13 9. State Diagrams . . . . . . . . . . . . . . . . . . 14 9.1. Client State Diagram . . . . . . . . . . . . . . 14 9.2. Session Manager State Diagram . . . . . . . . . 16 10. Protocol Encoding . . . . . . . . . . . . . . . . 17 10.1. Types . . . . . . . . . . . . . . . . . . . . . 18 10.2. Messages . . . . . . . . . . . . . . . . . . . 18 11. Predefined Properties . . . . . . . . . . . . . . 21 iii