This would be much more simplified, if you knew the proper version of yourself on ''the other side''. However that would mean to redesign the (private and proprietary) [[protocol]] to contain proper identification as a first sequence of its hand shake. Obviously I did similar mistake like [[PropertyFiles|our OSGi comrades]], and forget to include the version in the [[protocol]] at beginning.

This would be much more simplified, if you knew the proper version of yourself on ''the other side''. However that would mean to redesign the (private and proprietary) [[protocol]] to contain proper identification as a first sequence of its hand shake. Obviously I did similar mistake like [[PropertyFiles|our OSGi comrades]], and forget to include the version in the [[protocol]] at beginning.

Retrofitting a [[protocol]] to include its version later (and doing it [[BackwardCompatibility|backward compatibly]]) is indeed not easy. That is why I delayed changes to my [[protocol]] as much as I could. But yesterday I could not wait any longer and had to do it: [http://hg.netbeans.org/main-silver/rev/a44286c8cc96 see the patch]. All the beauty is gone. When new protocol tries to talk to old server, it may even reconnect to it twice. The first attempt to connect can be refused due to mutual misunderstanding. Then the second attempt is made using the older [[protocol]].

Retrofitting a [[protocol]] to include its version later (and doing it [[BackwardCompatibility|backward compatibly]]) is indeed not easy. That is why I delayed changes to my [[protocol]] as much as I could. But yesterday I could not wait any longer and had to do it: [http://hg.netbeans.org/main-silver/rev/a44286c8cc96 see the patch]. All the beauty is gone. When new protocol tries to talk to old server, it may even reconnect to it twice. The first attempt to connect can be refused due to mutual misunderstanding. Then the second attempt is made using the older [[protocol]] (which reminds me my [[Blogs:JaroslavTulach:Daily_Life:The_More_Languages|babylonian adventure with Europian languages]]).

Ugly, but since now things shall be well set for a [[evolution|future growth]]. Both sides of the communication can now adjust their capabilities to their mutual skills and select a vocabulary they both understand (see [http://hg.netbeans.org/main-silver/rev/0a75cd5c132e an example]).

Ugly, but since now things shall be well set for a [[evolution|future growth]]. Both sides of the communication can now adjust their capabilities to their mutual skills and select a vocabulary they both understand (see [http://hg.netbeans.org/main-silver/rev/0a75cd5c132e an example]).

=== Conclusion ===

=== Conclusion ===

When designing a [[protocol]], always make sure it contains a kind of hand shake or at minimum a version identification. Do it even if you are talking to ''yourself in a mirror''.

When designing a [[protocol]], always make sure it contains a kind of hand shake or at minimum a version identification. Do it even if you are talking to ''yourself in the mirror''.

<comments/>

<comments/>

[[Category:APITypes]]

[[Category:APITypes]]

=== The Version of Self ===

=== The Version of Self ===

One might think there are no [[protocol]] related problems and for a while I shared such false hope too. However there is a way to get into troubles. In spite this [[protocol]] being proprietary, used only by the [[NetBeans]] code, it may happen that different versions of [[NetBeans]] may share the same configuration directory and start to talk to each other. Now it is not ''just looking in a mirror''. Now you can see the ''man in the mirror'' with few years latency. And as [[protocols]] need to evolve from time to time (just like code and [[API]]s), you may find yourself trying to talk to really different version of ''self''.

One might think there are no [[protocol]] related problems in such situation and for a while I shared such false hope too. However there is a way to get into troubles. In spite this [[protocol]] being proprietary, used only by the [[NetBeans]] code, it may happen that different versions of [[NetBeans]] may share the same configuration directory and start to talk to each other. Now it is not ''just looking in a mirror''. Now you can see the ''man in the mirror'' with few years latency. And as [[protocols]] need to evolve from time to time (just like code and [[API]]s), you may find yourself trying to talk to really different version of ''self''.

This would be much more simplified, if you knew the proper version of yourself on ''the other side''. However that would mean to redesign the (private and proprietary) [[protocol]] to contain proper identification as a first sequence of its hand shake. Obviously I did similar mistake like [[PropertyFiles|our OSGi comrades]], and forget to include the version in the [[protocol]] at beginning.

This would be much more simplified, if you knew the proper version of yourself on ''the other side''. However that would mean to redesign the (private and proprietary) [[protocol]] to contain proper identification as a first sequence of its hand shake. Obviously I did similar mistake like [[PropertyFiles|our OSGi comrades]], and forget to include the version in the [[protocol]] at beginning.

=== The Version of Self ===

=== The Version of Self ===

One may think there are no [[protocol]] related problems and for a while I believed in the same false hope too. However there is a way to get into troubles. In spite this [[protocol]] being proprietary, used only by the [[NetBeans]] code, it may happen that different versions of [[NetBeans]] may share the same configuration directory and start to talk to each other. Now it is not ''just looking in a mirror''. Now you can see the ''man in the mirror'' with few years latency. And as [[protocols]] need to evolve from time to time (just like code and [[API]]s), you may find yourself trying to talk to really different version of ''self''.

One might think there are no [[protocol]] related problems and for a while I shared such false hope too. However there is a way to get into troubles. In spite this [[protocol]] being proprietary, used only by the [[NetBeans]] code, it may happen that different versions of [[NetBeans]] may share the same configuration directory and start to talk to each other. Now it is not ''just looking in a mirror''. Now you can see the ''man in the mirror'' with few years latency. And as [[protocols]] need to evolve from time to time (just like code and [[API]]s), you may find yourself trying to talk to really different version of ''self''.

This would be much more simplified, if you knew the proper version of yourself on ''the other side''. However that would mean to redesign the (private and proprietary) [[protocol]] to contain proper identification as a first sequence of its hand shake. Obviously I did similar mistake like [[PropertyFiles|our OSGi comrades]], and forget to include the version in the [[protocol]] at beginning.

This would be much more simplified, if you knew the proper version of yourself on ''the other side''. However that would mean to redesign the (private and proprietary) [[protocol]] to contain proper identification as a first sequence of its hand shake. Obviously I did similar mistake like [[PropertyFiles|our OSGi comrades]], and forget to include the version in the [[protocol]] at beginning.

For a while there has been an internal server listening on some local port inside every [[NetBeans]] application (I talked about it in [[Chapter 12]] too). This server guards access to files under configuration directory by ensuring that only one instance of [[NetBeans]] application is using such directory at a given time.

For a while there has been an internal server listening on some local port inside every [[NetBeans]] application (I talked about it in [[Chapter 12]] too). This server guards access to files under configuration directory by ensuring that only one instance of [[NetBeans]] application is using such directory at a given time.

In case another instance is started, it locates the proper port, contacts it and talks to it. So basically this is one instance of [[NetBeans]] talking to another instance of [[NetBeans]], both using the same bits. It is just ''like looking in a mirror''.

In case another instance is started, it locates the proper port, contacts it and talks to it. So basically this is one instance of [[NetBeans]] talking to another instance of [[NetBeans]], both using the same bits. It is just ''like looking in the mirror''.

=== The Version of Self ===

=== The Version of Self ===

[[Protocols]] are some what special among other [[APITypes]]: the amount of freedom when creating a protocol is really large. No restriction to group methods into classes and those in packages. No need to follow any existing grammar. At the end, every stream read or written to disk is an example of a [[protocol]]. And content of such streams can be very flexible.

[[Protocols]] are some what special among other [[APITypes]]: the amount of freedom when creating a protocol is really large. No restriction to group methods into classes and those in packages. No need to follow any existing grammar. At the end, every stream read or written to disk is an example of a [[protocol]]. And content of such streams can be very flexible.

These days the most common protocol is [[XML]] (which enforces a tree structure on the content of the stream), but one can still often find other (one could say ''legacy'') attempts to exchange information without relying on DTD, SOAP or Web Services. One such (and very flexible) form is based on [[PropertyFiles]]. But those who are dare enough can even use simple binary streams. Regardless the actual form, one principle shall always be followed: [[good]] [[protocols]] require the involved participants to ''introduce themselves'' first!

These days the most common (meta) [[protocol]] is [[XML]] (which enforces a tree structure on the content of the stream), but one can still often find other (one could say ''legacy'') attempts to exchange information without relying on DTD, SOAP or Web Services. One such (and very flexible) form is based on [[PropertyFiles]]. But those who are dare enough can even use simple binary streams. Regardless the actual form, one principle shall always be followed: [[good]] [[protocols]] require the involved participants to ''introduce themselves'' first!

=== Hand Shake First ===

=== Hand Shake First ===

[[Protocols]] are some what special among other [[APITypes]]: the amount of freedom when creating a protocol is really large. No restriction to group methods into classes and those in packages. No need to follow any existing grammar. At the end, every stream read or written to disk is an example of [[protocol]]. And content of such streams can be very flexible.

[[Protocols]] are some what special among other [[APITypes]]: the amount of freedom when creating a protocol is really large. No restriction to group methods into classes and those in packages. No need to follow any existing grammar. At the end, every stream read or written to disk is an example of a [[protocol]]. And content of such streams can be very flexible.

These days the most common protocol is [[XML]] (which enforces a tree structure on the content of the stream), but one can still often find other (one could say ''legacy'') attempts to exchange information without relying on DTD, SOAP or Web Services. One such (and very flexible) form is based on [[PropertyFiles]]. But those who are dare enough can even use simple binary streams. Regardless the actual form, one principle shall always be followed: [[good]] [[protocols]] require the involved participants to ''introduce themselves'' first!

These days the most common protocol is [[XML]] (which enforces a tree structure on the content of the stream), but one can still often find other (one could say ''legacy'') attempts to exchange information without relying on DTD, SOAP or Web Services. One such (and very flexible) form is based on [[PropertyFiles]]. But those who are dare enough can even use simple binary streams. Regardless the actual form, one principle shall always be followed: [[good]] [[protocols]] require the involved participants to ''introduce themselves'' first!

<comments/>

<comments/>

=== Conclusion ===

=== Conclusion ===

When designing a [[protocol]], always make sure it contains a kind of hand shake. Do it even if you are talking to ''yourself in a mirror''.

When designing a [[protocol]], always make sure it contains a kind of hand shake or at minimum a version identification. Do it even if you are talking to ''yourself in a mirror''.

<comments/>

<comments/>

One may think there are no [[protocol]] related problems and for a while I believed in the same false hope too. However there is a way to get into troubles. In spite this [[protocol]] being proprietary, used only by the [[NetBeans]] code, it may happen that different versions of [[NetBeans]] may share the same configuration directory and start to talk to each other. Now it is not ''just looking in a mirror''. Now you can see the ''man in the mirror'' with few years latency. And as [[protocols]] need to evolve from time to time (just like code and [[API]]s), you may find yourself trying to talk to really different version of ''self''.

One may think there are no [[protocol]] related problems and for a while I believed in the same false hope too. However there is a way to get into troubles. In spite this [[protocol]] being proprietary, used only by the [[NetBeans]] code, it may happen that different versions of [[NetBeans]] may share the same configuration directory and start to talk to each other. Now it is not ''just looking in a mirror''. Now you can see the ''man in the mirror'' with few years latency. And as [[protocols]] need to evolve from time to time (just like code and [[API]]s), you may find yourself trying to talk to really different version of ''self''.

This would be much more simplified, if you knew the proper version of yourself on ''the other side''. However that would mean to redesign the (private and proprietary) [[protocol]] to contain proper identification as a first sequence of its hand shake. Obviously I did similar mistake like [[PropertyFiles|our OSGi comrades]], and forget to include the version in the [[protocol]] at beginning. Retrofitting the [[protocol]] to include the version later (and doing it [[BackwardCompatibility|backward compatibly]]) is indeed not easy. That is why I delayed changes to my [[protocol]] as much as I could. But yesterday I could not wait any longer and had to do it: [http://hg.netbeans.org/main-silver/rev/a44286c8cc96 see the patch]. All the beauty is gone, when new protocol tries to talk to old server, it may even require to connect to it twice, but since now things shall be OK. Both sides of the communication can adjust their capabilities to their mutual skills and select a vocabulary they both understand (see [http://hg.netbeans.org/main-silver/rev/0a75cd5c132e an example]).

This would be much more simplified, if you knew the proper version of yourself on ''the other side''. However that would mean to redesign the (private and proprietary) [[protocol]] to contain proper identification as a first sequence of its hand shake. Obviously I did similar mistake like [[PropertyFiles|our OSGi comrades]], and forget to include the version in the [[protocol]] at beginning.

 

Retrofitting a [[protocol]] to include its version later (and doing it [[BackwardCompatibility|backward compatibly]]) is indeed not easy. That is why I delayed changes to my [[protocol]] as much as I could. But yesterday I could not wait any longer and had to do it: [http://hg.netbeans.org/main-silver/rev/a44286c8cc96 see the patch]. All the beauty is gone. When new protocol tries to talk to old server, it may even reconnect to it twice. The first attempt to connect can be refused due to mutual misunderstanding. Then the second attempt is made using the older [[protocol]].

 

Ugly, but since now things shall be well set for a [[evolution|future growth]]. Both sides of the communication can now adjust their capabilities to their mutual skills and select a vocabulary they both understand (see [http://hg.netbeans.org/main-silver/rev/0a75cd5c132e an example]).

=== Conclusion ===

=== Conclusion ===