SIP Communication

SIP generally communicates over a TCP connection (either raw sockets or over telnet), but can also communicate via serial connections and other methods. In Evergreen, the most common deployment is a RAW socket connection on port 6001.

SIP communication consists of strings of messages, each message request and response begin with a 2-digit “command” - Requests usually being an odd number and responses usually increased by 1 to be an even number. The combination numbers for the request command and response is often referred to as a Message Pair (for example, a 23 command is a request for patron status, a 24 response is a patron status, and the message pair 23/24 is patron status message pair). The table in the next section shows the message pairs and a description of them.

For clarification, the “Request” is from the device (selfcheck or otherwise) to the ILS/ACS. The response is… the response to the request ;).

Within each request and response, a number of fields (either a fixed width or separated with a | [pipe symbol] and preceded with a 2-character field identifier) are used. The fields vary between message pairs.






Block Patron


01/Block_Patron - ACS responds with 24 Patron Status Response



Yes (with extensions)




Yes (no renewals)




Partially supported



Item Information

Yes (no extensions)



Item Status Update


19/20_Item_Status_Update - Returns Patron Enable response, but doesn’t make any changes in EG


Patron Status


23/24_Patron_Status - 63/64 “Patron Information” preferred


Patron Enable


25/26_Patron_Enable - Used during system testing and validation






End Session




Fee Paid




Patron Information

Yes (no extensions)



Renew All






93/94_Login - Must be first command to Evergreen ACS (via socket) or SIP will terminate


Resend last message




SC-ACS Status



01 Block Patron

A selfcheck will issue a Block Patron command if a patron leaves their card in a selfcheck machine or if the selfcheck detects tampering (such as attempts to disable multiple items during a single item checkout, multiple failed pin entries, etc).

In Evergreen, this command does the following:

  • User alert message: CARD BLOCKED BY SELF-CHECK MACHINE (this is independent of the AL Blocked Card Message field).
  • Card is marked inactive.

The request looks like:

01<card retained><date>[fields AO, AL, AA, AC]

Card Retained: A single character field of Y or N - tells the ACS whether the SC has retained the card (ex: left in the machine) or not.

Date: An 18 character field for the date/time when the block occurred.

Format: YYYYMMDDZZZZHHMMSS (ZZZZ being zone - 4 blanks when local time, “Z” (3 blanks and a Z) represents UTC(GMT/Zulu)

Fields: See Fields for more details.

The response is a 24 “Patron Status Response” with the following:

  • Charge privileges denied
  • Renewal privileges denied
  • Recall privileges denied (hard-coded in every 24 or 64 response)
  • hold privileges denied
  • Screen Message 1 (AF): blocked
  • Patron

09/10 Checkin

~The request looks like:

09<No block (Offline)><xact date><return date>[Fields AP,AO,AB,AC,CH,BI]

No Block (Offline): A single character field of Y or N - Offline transactions are not currently supported so send N.

xact date: an 18 character field for the date/time when the checkin occurred. Format: YYYYMMDDZZZZHHMMSS (ZZZZ being zone - 4 blanks when local time, “Z” (3 blanks and a Z) represents UTC(GMT/Zulu)

Fields: See Fields for more details.

The response is a 10 “Checkin Response” with the following:

10<resensitize><magnetic media><alert><xact date>[Fields AO,AB,AQ,AJ,CL,AA,CK,CH,CR,CS,CT,CV,CY,DA,AF,AG]

Example (with a remote hold):

09N20100507    16593720100507    165937APCheckin Bin 5|AOBR1|AB1565921879|ACsip_01|
101YNY20100623    165731AOBR1|AB1565921879|AQBR1|AJPerl 5 desktop reference|CK001|CSQA76.73.P33V76 1996
|CTBR3|CY373827|DANicholas Richard Woodard|CV02|

Here you can see a hold alert for patron CY 373827, named DA Nicholas Richard Woodard, to be picked up at CT “BR3”. Since the transaction is happening at AO “BR1”, the alert type CV is 02 for hold at remote library. The possible values for CV are:

  • 00: unknown
  • 01: local hold
  • 02: remote hold
  • 03: ILL transfer (not used by EG)
  • 04: transfer
  • 99: other


The logic for Evergreen to determine whether the content is magnetic_media comes from either legacy circ scripts or search_config_circ_modifier. The default is non-magnetic. The same is true for media_type (default 001). Evergreen does not populate the collection_code because it does not really have any, but it will provide the call_number where available.

Unlike the item_id (barcode), the title_id is actually a title string, unless the configuration forces the return of the bib ID.

Don’t be confused by the different branches that can show up in the same response line.

  • AO is where the transaction took place,
  • AQ is the “permanent location”, and
  • CT is the destination location (i.e., pickup lib for a hold or target lib for a transfer).

11/12 Checkout

15/16 Hold

Evergreen supports the Hold message for the purpose of canceling holds. It does not currently support creating hold requests via SIP2.

17/18 Item Information

The request looks like:

17<xact_date>[fields: AO,AB,AC]

The request is very terse. AC is optional.

The following response structure is for SIP2. (Version 1 of the protocol had only 6 total fields.)



1720060110    215612AOBR1|ABno_such_barcode|
1801010120100609    162510ABno_such_barcode|AJ|
1720060110    215612AOBR1|AB1565921879|
1810020120100623    171415AB1565921879|AJPerl 5 desktop reference|CK001|AQBR1|APBR1|BGBR1
|CTBR3|CSQA76.73.P33V76 1996|

The first case is with a bogus barcode. The latter shows an item with a circulation_status of 10 for in transit between libraries. The known values of circulation_status are enumerated in the spec.

EXTENSIONS: The CT field for destination location and CS call number are used by Automated Material Handling systems.

19/20 Item Status Update

23/24 Patron Status


2300120060101    084235AOUWOLS|AAbad_barcode|ACsip_01|ADbad_password|
24YYYY          00120100507    013934AE|AAbad_barcode|BLN|AOUWOLS|
2300120060101    084235AOCONS|AA999999|ACsip_01|ADbad_password|
24  Y           00120100507    022318AEDoug Fiander|AA999999|BLY|CQN|BHUSD|BV0.00|AFOK|AOCONS|
2300120060101    084235AOCONS|AA999999|ACsip_01|ADuserpassword|LY|CQN|BHUSD|BV0.00|AFOK|AOCONS|
24  Y           00120100507    022803AEDoug Fiander|AA999999|BLY|CQY|BHUSD|BV0.00|AFOK|AOCONS|
  1. The BL field (SIP2, optional) is valid patron, so the N value means bad_barcode doesn’t match a patron, the Y value means 999999 does.
  2. The CQ field (SIP2, optional) is valid password, so the N value means bad_password doesn’t match 999999’s password, the Y means userpassword does.

So if you were building the most basic SIP2 authentication client, you would check for |CQY| in the response to know the user’s barcode and password are correct (|CQY| implies |BLY|, since you cannot check the password unless the barcode exists). However, in practice, depending on the application, there are other factors to consider in authentication, like whether the user is blocked from checkout, owes excessive fines, reported their card lost, etc. These limitations are reflected in the 14-character patron status string immediately following the 24 code. See the field definitions in your copy of the spec.

25/26 Patron Enable

Not yet supported.

29/30 Renew

Evergreen supports the Renew message.

35/36 End Session

3520100505    115901AOBR1|AA999999|
36Y20100507    161213AOCONS|AA999999|AFThank you!|

The Y/N code immediately after the 36 indicates success/failure. Failure is not particularly meaningful or important in this context, and for evergreen it is hardcoded Y.

37/38 Fee Paid

Evergreen supports the Fee Paid message.

63/64 Patron Information

Attempting to retrieve patron info with a bad barcode:

6300020060329    201700          AOBR1|AAbad_barcode|
64YYYY          00020100623    141130000000000000000000000000AE|AAbad_barcode|BLN|AOBR1|

Attempting to retrieve patron info with a good barcode (but bad patron password):

6300020060329    201700          AOBR1|AA999999|ADbadpwd|
64  Y           00020100623    141130000000000000000000000000AA999999|AEDavid J. Fiander|BHUSD|BV0.00
|BD2 Meadowvale Dr. St Thomas, ON Canada
90210||BF(519) 555 1234|AQBR1|BLY|CQN|PB19640925|PCPatrons

See 23/24 Patron Status for info on BL and CQ fields.

65/66 Renew All

Evergreen supports the Renew All message.

93/94 Login


[Connection closed by foreign host.]

941 means successful terminal login. 940 or getting dropped means failure.

97/96 Resend

99/98 SC and ACS Status

99<status code><max print width><protocol version>

All 3 fields are required:

  • 0: SC is OK
  • 1: SC is out of paper
  • 2: SC shutting down
  • status code - 1 character
  • max print width - 3 characters - the integer number of characters the client can print
  • protocol version - 4 characters - x.xx

    98<on-line status><checkin ok><checkout ok><ACS renewal policy>
    <status update ok><offline ok><timeout period>
    <retries allowed><date/time sync><protocol version><institution id>
    <library name><supported messages><terminal
    location><screen message><print line>


98YYYYNN60000320100510    1717202.00AOCONS|BXYYYYYYYYYNYNNNYN|

The Supported Messages field BX appears only in SIP2, and specifies whether 16 different SIP commands are supported by the ACS or not.


All fixed-length fields in a communication will appear before the first variable-length field. This allows for simple parsing. Variable-length fields are by definition delimited, though there will not necessarily be an initial delimiter between the last fixed-length field and the first variable-length one. It would be unnecessary, since you should know the exact position where that field begins already.