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Manuals: slink2ew

On startup, slink2ew reads the configuration file named on the command line. Commands in this file set all the parameters used for configuring the Earthworm SeedLink client module. In the control file, lines may begin with a valid slink2ew command (listed below) or with one of 2 special characters:

# marks the line as a comment (example: # This is a comment).
@ allows control files to be nested; one control file can be accessed from another with the command “@” followed by a string representing the path name of the next control file (example: @model.d).

Command names must be typed in the control file exactly as shown in this document (commands are case sensitive). Blank lines are also permitted in the control file.

The SeedLink protocol was originally developed at GEOFON as a component of the Seismological Communication Processor, or SeisComP.

1. Functional command listing

Below are the commands recognized by slink2ew, grouped by the function they influence. Most of the commands are required; they may be specified in any order in the control file.

Command Description
Earthworm system setup
MyModuleId required
RingName required
HeartBeatInterval required
Verbosity optional
SeedLink server and connection parameters
SLaddr required
SLport required
Selectors optional
Stream optional
NetworkTimeout optional
NetworkDelay optional
KeepAlive optional
MaxRate optional
ForceTraceBuf1 optional (slink2ew >= 1.1)
instId optional
Output control
LogFile required
StateFile optional
StateFileInt optional

2. Alphabetic command listing & description

In the following section, all configuration file commands are listed in alphabetical order. Listed along with the command are its arguments, the name of the subroutine that processes the command, and the function within the module that the command influences. A detailed description of the command and is also given. Default values and example commands are listed after each command description.

Command Arg Processed by In function Description
ForceTraceBuf1 switch ReadConfig Earthworm setup Sets the on-off switch to force the creation of TRACEBUF messages on systems that support TRACEBUF2 messages. By default, the module will create TRACEBUF2 messages on systems that support them otherwise it will create the older TRACEBUF messages. This switch has no effect on systems that do no support TRACEBUF2 messages. This switch could be useful in environments where a transition is occurring between TRACEBUF and TRACEBUF2 messages, otherwise most people will never use this.

Default: 0 (disabled)
Example: ForceTraceBuf1 1
HeartBeatInterval interval ReadConfig Earthworm setup Defines the interval in seconds at which the module will issue TYPE_HEARTBEAT messages.

Default: none
Example: HeartBeatInterval 30
LogFile switch ReadConfig Earthworm setup Sets the on-off switch for writing a log file to disk. If switch is 0, no log file will be written. If switch is 1, coaxtoring will write a daily log file(s) called coaxtoringxx.log_yymmdd where xx is coaxtoring’s module id (set with MyModuleId command) and yymmdd is the current UTC date (ex: 960123) on the system clock. The file(s) will be written in the EW_LOG directory (environment variable). If switch is 2 the log file is written but output to stdout and stderr is suppressed.

Default: none
Example: LogFile 1
KeepAlive interval ReadConfig Data Selection Specifies the interval in seconds that the module will send keep alive (heartbeat) packets to the remote SeedLink server. A value of 0 disables the feature. This feature only works with versions of SeedLink 2.93 or greater. This is useful for keeping a network connection open that might be closed by intermediate firewalls/gateways when the data stream only flows at intervals.

Default: 0 (disabled)
Example: KeepAlive 600
MaxRate rate ReadConfig Earthworm setup Specifies the maximum rate in bytes per second that the module will receive data and generate TraceBuf packets. A value of 0 disables the feature. This is useful for limiting the rate that TraceBuf packets are forwarded to the local system. In particular, during times of backfill data may be delivered by the upstream server faster than the local system can process the packets.

Default: 0 (disabled, no rate limit)
Example: MaxRate 204800 (i.e. 200 kilobytes/second)
instId ID ReadConfig Earthworm setup Override the installation ID included in TraceBuf packets. By default the installation ID is that of the local system as defined by the EW_INSTALLATION environment variable. This option is useful for specifying the installation ID of the remote system providing the data or simply to avoid inserting the local ID.

Default: (Local Installation ID)
Example: instId INST_UNKNOWN
MyModuleId mod_id ReadConfig Earthworm setup Sets the module id for labeling all outgoing trigger, heartbeat, and error messages. mod_id is a character string (valid strings are listed in earthworm.d) that relates to a unique single-byte number.

Default: none
Example: MyModuleId MOD_SLINK2EW_GE
NetworkDelay delay ReadConfig Earthworm setup Sets the re-connection delay in seconds. After the connection to the remote SeedLink server has been broken (network timeout or any other connection problems) the module will wait this many seconds before attempting to re-connect.

Default: 30
Example: NetworkDelay 10
NetworkTimeout timeout ReadConfig Earthworm setup Sets the network timeout in seconds. If the module has not received any packets from the remote SeedLink server in this amount of time the connection will be closed and re-opened if possible. A value of 0 disables this feature.

Default: 600
Example: NetworkTimeout 300
RingName ring ReadConfig Earthworm setup Indicates which shared memory region to use for waveform output. ring is a character string (valid strings are listed in earthworm.d) that relates (in earthworm.d) to a unique number for the key to the shared memory region.

Default: none
Example: RingName WAVE_RING
Selectors selectors ReadConfig Data selection Specify the SeedLink selectors for uni-station mode or default selectors for multi-station mode. Multiple selectors must be enclosed by quotes. If Stream commands are also specified in the command file, implying multi-station mode, any selectors specified with this command will be used as defaults when no data stream selectors are specified with a given Stream command.

Default: none
Example: Selectors "BH?.D LH?.D"
SLaddr address ReadConfig SeedLink parameters Specify the address of the SeedLink server. This can be either on IP address (four period-separated numbers) or the domain name of the server.

Default: none
Example: SLaddr
SLport port ReadConfig SeedLink parameters Specifies the IP port number for the SeedLink server. This is commonly 18000.

Default: none
Example: SLport 18000
StateFile [filename] ReadConfig Earthworm setup If this flag is specified a file with a list of sequence numbers is written, during a clean module shutdown, to the parameter directory with the name "slink<mod id>.state". Alternatively, a filename may be specified. During module startup these sequence numbers are used to resume data streams from the last received data. In this way continuous data can be collected even through system restarts. If this flag is not set the module will always request the next available data. Using this functionality is highly recommended unless you know that it is not necessary.

Default: none
Example: StateFile
StateFileInt interval ReadConfig Earthworm setup This option specifies the interval for saving the state file in number of packets received. In otherwords, using the default interval of 100, the statefile will be updated every 100 packets received. The purpose of this functionality is to minimize the amount of duplicate data collected if the module is ever killed without saving the current state information.

Default: 100
Example: StateFileInt 500
Stream streamkey [selectors] ReadConfig@ Data selection Specifies one stream of data to be requested from the remote SeedLink server. This command implies the use of multi-station mode and can be specified multiple times to requested multiple data streams. The streamkey is composed of a network and station code separated by an underscore. Optional SeedLink selectors may be specified after the stream key. Multiple selectors must be enclosed in quotes. Beware of collecting multiple data streams with the same station code and differing location codes as the rest of Earthworm does not know about location codes, so the two data streams would get mixed together with bad results.

Default: none
Example: Stream GE_DSB "BH?.D HH?.D"
Verbosity level ReadConfig Earthworm setup Specifies the level of logging verbosity. Level 0 is rather quiet and mostly reports errors, level 1 shows negotiation details and every received packet and level 2 shows a lot of details.

Default: 0
Example: Verbosity 0

3. Advanced Description

The SeedLink protocol allows two different modes of data transfer. All or uni-station mode is the method used for transmitting all stations from a node. In this case the client does not specify a stream key (network and station code) as the data stream is implied to be whatever is available from the server. Multi-station mode is the method used for requesting multiple, selected data streams (stations). All/Uni-station mode is supported by all current SeedLink versions. Multi-station mode is supported by SeedLink 2.5 or later (SeisComP-1.1.6 or later).

For slink2ew the presence of one or more Stream commands in the configuration file triggers multi-station mode. Otherwise the module defaults to all/uni-station mode.

SeedLink selectors are used to request specific types of data within a given data stream, in effect limiting the default action of sending all data types. A data packet is sent to the client if it matches any positive selector (without leading !) and doesn’t match any negative selectors (with a leading !). The general format of selectors is LLSSS.T, where LL is location, SSS is channel and T is type (one of [DECOTL] for Data, Event, Calibration, Blockette, Timing, and Log records). LL, .T, and LLSSS. can be omitted, implying anything in that field. It is also possible to use ? in place of L and S as a single character wildcard. Multiple selectors are separated by space(s).

Some examples:

BH? BHZ, BHN, BHE (all record types)
00BH?.D BHZ, BHN, BHE with location code 00 (data records)
BH? !E BHZ, BHN, BHE (excluding detection records)
BH? E BHZ, BHN, BHE & detection records of all channels
!LCQ !LEP exclude LCQ and LEP channels
!L !T exclude log and timing records

For slink2ew only data records will be written to the ring. In other words, requesting any records in addition to data records is a waste and you should always append .D to any specified selectors.

4. Sample Configuration File

#                     Configuration File for slink2ew
MyModuleId       MOD_SLINK2EW
RingName         WAVE_RING       # Transport ring to write output to.
HeartBeatInterval     30         # Heartbeat interval, in seconds.
LogFile               1          # 1 -> Keep log, 0 -> no log file
                                 # 2 -> write to module log but not stderr/stdout
#Verbosity      0                # Set level of verbosity.
SLhost   # Host address of the SeedLink server
SLport         18000             # Port number of the SeedLink server
StateFile      slink2ew.GE       # File with a list of sequence numbers which
                                 # is read during module startup to resume
                                 # data streams.  This file is written on a
                                 # clean module shutdown.  If this is not
                                 # specified as an absolute path the value of
                                 # the environment variable EW_PARAMS will
                                 # be pre-pended to this value.  Using this
                                 # functionality is highly recommended.
#NetworkTimeout 600              # Network timeout, after this many idle
                                 # seconds the connection will be reset.
                                 # Default is 600 seconds, 0 to disable.
#NetworkDelay   30               # Network re-connect delay in seconds.
#KeepAlive      0                # Send keepalive packets (when idle) at this
                                 # interval in seconds.  Default is 0 (disabled).
#ForceTraceBuf1 0                # On systems that support TRACEBUF2
                                 # messages this flag will force the module
                                 # to create TRACEBUF messages instead.
                                 # Most people will never need this.
# Selectors and Stream's.  If any Stream lines are specified the connection
# to the SeedLink server will be configured in multi-station mode using
# Selectors, if any, as defaults.  If no Stream lines are specified the
# connection will be configured in uni-station mode using Selectors, if any.
Selectors      "BH?.D"           # SeedLink selectors.  These selectors are used
                                 # for a uni-station mode connection.  If one
                                 # or more 'Stream' entries are given these are
                                 # used as default selectors for multi-station
                                 # mode data streams.  See description of
                                 # SeedLink selectors below.  Multiple selectors
                                 # must be enclosed in quotes.
# List each data stream (a network and station code pair) that you
# wish to request from the server with a "Stream" command.  If one or
# more Stream commands are given the connection will be configured in
# multi-station mode (multiple station data streams over a single
# network connection).  If no Stream commands are specified the
# connection will be configured in uni-station mode, optionally using
# any specified "Selectors".  A Stream command should be followed by a
# stream key, a network code followed by a station code separated by
# an underscore (i.e. IU_KONO).  SeedLink selectors for a specific
# stream may optionally be specified after the stream key.  Multiple
# selectors must be enclosed in quotes.  Any selectors specified with
# the Selectors command above are used as defaults when no selectors
# are specified for a given stream.
# Combined with the above specified default selectors the BHx channels
# will be requested for each of these stations except for DSB for which
# we also want the LHx channels.
Stream  GE_DSB   "BH?.D LH?.D"
Stream  GE_ISP
Stream  GE_APE
Stream  GE_STU
# Some SeedLink servers support extended selection capability allowing
# wildcards (either '*' or '?') in the network and station fields, for example
# to select all stations from the TA network:
Stream TA_*

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