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i-scream Protocols |
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================== |
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|
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Contents |
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-------- |
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- Conventions |
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|
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- Host Connection Protocol |
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- Host Heartbeat Protocol |
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- Host Data Protocol |
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|
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- Client Control Protocol |
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- Client Data Protocol |
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|
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|
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Conventions |
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----------- |
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All protocols in this document assume a valid connection of |
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the appropriate type has been made, and that data streams |
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are already available. All strings should, and will be, |
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terminated with a \n (newline character) to indicate the end |
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of the message. All messages are sent as ASCII Strings. |
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|
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Fixed protocol messages will appear in [] brackets, if there |
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is a variety of options they will be separated with the | |
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character. For example: |
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|
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[OK|ERROR] |
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|
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Indicates that the message "OK" OR the message "ERROR" will |
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be sent depending on the result of the last action. |
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|
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Data messages will appear in {} brackets, where the name in |
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the brackets indicates the type (as in kind, not data type) |
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of data that will be returned. For example: |
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|
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{lastmodified} |
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|
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Indicates that data for use as 'last modified' will be |
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returned. |
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|
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If [ERROR] is sent back at any time, this indicates that all |
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communication is over. EXCEPT where otherwise specified! |
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|
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|
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Host Connection Protocol |
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------------------------ |
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The initial connection of a host to the i-scream server is |
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through the FilterManager. A Host gets its configuration |
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and then gets assigned a Filter to connect to and start |
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sending data. |
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|
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The port number of the FilterManager is fully configurable, |
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however the default at this time is 4567. |
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|
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Host (direction) Server Comment |
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------------------------------------------------------------ |
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[STARTCONFIG]----------> Requests to start |
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receiving config |
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information |
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|
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<---------- [OK|ERROR] If the server ok's |
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the request or not |
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|
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[LASTMODIFIED]----------> Asks when the config |
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was last modified |
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(used when checking |
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if the config has |
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changed) |
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|
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<---------- [{lastmodified}Returns a long int |
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|ERROR] time since epoch |
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eg, 123456789 |
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To indicate what |
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format this is in, |
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I quote from the |
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Java 1.3 JDK API |
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"measured in milli |
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-seconds since the |
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epoch" |
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|
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[FILELIST] ----------> Asks the server for |
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the list of files |
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that were used to |
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build the config |
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(used when checking |
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if the config has |
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changed) |
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|
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<---------- [{filelist} Returns a semi-colon |
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|ERROR] separated list of |
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filenames |
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eg, |
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a.conf;b.conf;c.conf |
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|
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********** LOOP START ********** |
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This loop reads configuration |
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properties from the config |
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|
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[{property}] ----------> Sends the name of a |
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property to be |
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retrieved from the |
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config file |
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eg, UDPUpdateTime |
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|
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<---------- [{value}|ERROR]Returns the value of |
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the requested config |
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property |
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eg, 120 |
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If it is unable to |
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find the requested |
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property it returns |
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ERROR to indicate |
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that fact, but |
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communication still |
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proceeds |
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|
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********** LOOP UNTIL ********** |
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The loop continues until the host |
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sends the following message |
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|
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[ENDCONFIG] ----------> Indicates that the |
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host requires no |
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more config |
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|
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********** LOOP END ********** |
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Communication continues |
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|
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<---------- [OK] Indicates that the |
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server is ready to |
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proceed |
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|
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[FILTER] ----------> Asks the server to |
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send it the host |
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information of a |
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filter that it |
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should connect to |
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|
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<---------- {filter} Returns a semi-colon |
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separated list of |
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FQDN hostname, UDP |
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port number and TCP |
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port number that a |
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configured Filter is |
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running on and |
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assigned to the |
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calling host |
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eg, |
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raptor.ukc.ac.uk; |
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1234;5678 |
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|
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[END] ----------> Indicates to the |
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server that the host |
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has finished an will |
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disconnect |
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|
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<---------- [OK|ERROR] Indicates that the |
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server is either ok |
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or that it thought |
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there was an error |
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------------------------------------------------------------ |
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|
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Host Heartbeat Protocol |
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----------------------- |
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When a host is configured after it has connected it should |
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obtain a property TCPUpdateTime. This indicates how often |
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a host should send a "Heart Beat", which is a pro-active |
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connection to the server by the host to indicate that it is |
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still alive. This "Heart Beat" also allows a host to see |
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its configuration has changed and act accordingly. In a |
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well written host this should just be a case of dropping out |
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of a loop and heading back to the start (connecting to the |
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filter manager). |
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|
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Host (direction) Server Comment |
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------------------------------------------------------------ |
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[HEARTBEAT] ----------> Starts the |
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heartbeat protocol |
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off |
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|
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<---------- [OK|ERROR] Indicates that the |
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server is ok or not |
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|
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[CONFIG] ----------> Indicates that the |
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host wants to check |
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its config |
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|
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<---------- [OK|ERROR] Indicates that the |
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server is ok or not |
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|
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[{filelist}] ----------> Send a semi-colon |
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separated list of |
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filenames |
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eg, |
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a.conf;b.conf;c.conf |
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This should be |
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identical to the one |
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received in the |
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connection protocol |
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|
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<---------- [OK] Indicates that the |
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server is ok |
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|
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[{lastmodified}]----------> Returns a long int |
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time since epoch |
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eg, 123456789 |
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This should be |
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identical to the one |
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received in the |
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connection protocol |
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To indicate what |
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format this is in, |
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I quote from the |
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Java 1.3 JDK API |
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"measured in milli |
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-seconds since the |
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epoch" |
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|
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<---------- [OK|ERROR] The server then |
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checks all the files |
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in the file list to |
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see if they have |
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been modified more |
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recently than the |
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lastmodified value. |
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If they HAVE that |
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indicates that the |
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configuration has |
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changed and the host |
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should re-configure, |
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thus it sends ERROR. |
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If the files remain |
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unchanged the server |
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will return OK to |
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indicate the host |
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should continue as |
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before |
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|
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[ENDHEARTBEAT] ----------> Indicates to the |
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server that the host |
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has finished an will |
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disconnect |
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|
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<---------- [OK|ERROR] Indicates that the |
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server is either ok |
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or that it thought |
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there was an error |
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------------------------------------------------------------ |
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|
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Host Data Protocol |
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------------------ |
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The UDP data packets that are sent by the host contain |
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simply XML data. For information on the format of this |
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data see the XML via UDP specification document at: |
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|
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http://www.i-scream.org.uk/cgi-bin/docs.cgi?doc=specification/xml_via_udp.txt |
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|
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Client Control Protocol |
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----------------------- |
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|
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The client control protocol channel is opened by the client |
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and allows a variety of actions to be carried out by the |
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client at anytime. Unlike previous protocols, this is NOT |
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sequential, all of the requests can be carried out in |
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any order. |
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|
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All client protocols are backwards compatible, and the |
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version is shown by the protocol identifier. |
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|
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There are three sections to this protocol. |
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|
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1) Initialise (sent only at start) |
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2) Send command(s) - unlimited number in any order |
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3) Disconnect (sent only at end) |
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|
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If at anytime the client sends something the server does |
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not understand, an [ERROR] will be sent |
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|
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All are indicated with <> brackets. |
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|
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v1.0 - Protocol identifier: "PROTOCOL 1.0" (without quotes) |
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Supported commands: |
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STARTCONFIG |
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STARTDATA |
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STOPDATA |
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|
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Host (direction) Server Comment |
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------------------------------------------------------------ |
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<initialise> |
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[CONNECT] ----------> Starts off the |
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client protocol |
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|
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<---------- [{protocol}] The server sends the |
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protocol identifier |
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|
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[{name}] ----------> The client sends its |
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"name". This name |
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is used to identify |
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the type of client |
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to the system and |
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obtain its config |
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eg, Conient |
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|
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<---------- [OK] Indicates the server |
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is ok to proceed |
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|
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|
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<command #1> (allows client to obtain its configuration) |
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[STARTCONFIG]----------> Tell the server we |
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want to start this |
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command |
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|
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<---------- [OK] Indicates the server |
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is ok to proceed |
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|
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********** LOOP START ********** |
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This loop reads configuration |
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properties from the config |
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|
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[{property}] ----------> Sends the name of a |
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property to be |
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retrieved from the |
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config file |
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Clients can obtain |
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host information |
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eg, |
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Host.UDPUpdateTime |
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Otherwise it must |
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prefix requests |
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with "Client." |
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All other requests |
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will be ignored as |
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if it was unable to |
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retieve the property |
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|
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<---------- [{value}|ERROR]Returns the value of |
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the requested config |
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property |
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eg, 120 |
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If it is unable to |
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find the requested |
| 342 |
property it returns |
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ERROR to indicate |
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that fact |
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|
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********** LOOP UNTIL ********** |
| 347 |
The loop continues until the client |
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sends the following message |
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|
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[ENDCONFIG] ----------> Indicates that the |
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client requires no |
| 352 |
more config |
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|
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********** LOOP END ********** |
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Communication continues |
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|
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<---------- [OK] Indicates that the |
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server is ready to |
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proceed |
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|
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<command #2> (tells the server to start the data link) |
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[STARTDATA] ----------> Tell the server we |
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want to start this |
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command |
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|
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<---------- [{portnumber} The server then sets |
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|ERROR] itself listening for |
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a connection on its |
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data link socket for |
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this client. It |
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returns the port no. |
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that it is listening |
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on eg, 12367 |
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If the data link is |
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yet to be started |
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the server will |
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return ERROR |
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|
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<---------- [OK] Indicates the server |
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is ok to proceed and |
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the client can |
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then connect its |
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data link |
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|
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<command #3> (tells the server to stop the data link) |
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[STOPDATA] ----------> Tell the server we |
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want to start this |
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command |
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The server then |
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shuts down the |
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data link to the |
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client |
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|
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<---------- [OK|ERROR] Returns OK is the |
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server is ready to |
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proceed, or ERROR |
| 397 |
if the data link |
| 398 |
was not open in the |
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first place |
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|
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<disconnect> |
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[DISCONNECT] ----------> Tells the server the |
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client wants to |
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close the control |
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link |
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|
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<---------- [OK] The last word from |
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the server, it will |
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disappear after this |
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------------------------------------------------------------ |
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|
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v1.1 - Protocol identifier: "PROTOCOL 1.1" (without quotes) |
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Supported commands: |
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SETHOSTLIST |
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|
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Host (direction) Server Comment |
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------------------------------------------------------------ |
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<command #4> (indicates to the server which hosts the client |
| 419 |
wants data from) |
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[SETHOSTLIST]----------> Tell the server we |
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want to start this |
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command |
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|
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<---------- [OK|ERROR] The server will |
| 425 |
return an ERROR if |
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the data link is |
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open, as a host list |
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must ONLY be set |
| 429 |
if the data link is |
| 430 |
closed |
| 431 |
If the server is |
| 432 |
ok to proceed with |
| 433 |
the command it says |
| 434 |
[OK] |
| 435 |
|
| 436 |
[{hostlist}] ----------> This is a semi-colon |
| 437 |
seperated list of |
| 438 |
FQDN hostnames that |
| 439 |
the client wishes to |
| 440 |
recieve data from |
| 441 |
eg, |
| 442 |
raptor.ukc.ac.uk;killigrew.ukc.ac.uk;chalk.ukc.ac.uk |
| 443 |
|
| 444 |
If the list is sent |
| 445 |
blank (or if no list |
| 446 |
is set at all) then |
| 447 |
data from ALL hosts |
| 448 |
will be sent to the |
| 449 |
client |
| 450 |
|
| 451 |
<---------- [OK] Indicates the server |
| 452 |
is ok to proceed and |
| 453 |
the host list has |
| 454 |
been accepted |
| 455 |
------------------------------------------------------------ |
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|
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Client Data Protocol |
| 458 |
-------------------- |
| 459 |
Once the data link has been opened by the control link, the |
| 460 |
server will send XML formated data packets seperated by the |
| 461 |
\n (newline) character. For information on the format of |
| 462 |
this data see the XML via UDP specification document at: |
| 463 |
|
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http://www.i-scream.org.uk/cgi-bin/docs.cgi?doc=specification/xml_via_udp.txt |
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|
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About |
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----- |
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This document was written by AJ Moore [ajm4@ukc.ac.uk] for |
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use by the team working on a 3rd year Computer Science |
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project called "i-scream". More details can be found on the |
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project website; |
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|
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http://www.i-scream.org.uk |
