As soon as HL7 communication involves networks, security is an issue. We do not want everybody in the world to admit or discharge patients, nor do we allow any site in our institution to send any type of a message. In order to control access to the TCP/IP networked HL7 services, a special access control list is used that allows to specify access to services depending on:
The `hl7hosts' file is a simple table where each line represents one access control entry that specifies the above attributes. Fields are separated by blank characters. Comment lines starting with a number sign (`#') are allowed as well as blank lines. Lines that start with a blank character (i.e. space or tab) are continuations of the preceding line. Asterisks (`*') allow any value to match the respective attribute. Lists of message types are specified using the `message^event' notation each entry of the list separated by blanks. The first entry of the list may have a `+' or `-' prepended specifying the sense of the list: a `+' means that the list specifies allowed messages while the `-' means that all message except those specified are allowed. No sign implies `+' and an empty list at all means all message types.
# host cid SenApp SenFac RecApp RecFac Messages
#-------- -- -------- -------- --------- -------- -----------------
localhost * TEST_APP TEST_FAC * * NMD
localhost * * * * *
uks3p * * * NSERVER ANAE +NMD ORU
uks3p * * * CVGATEWAY 060_IOP
uks3p * * * * * +NMD ACK ADT^A01 ADT^A02
ADT^A03 ORU
* * * * HL7TEST *
section The HL7 to CareVue Gateway Program.