HTTP Health Monitor in LTM

Receive String - which documentation did you use for that? the | means or, it is either 200 or OK. which you probably don't want. if you are just looking for HTTP return code 200 then HTTP/1.1 200 OK is fine. for the others it is more difficult to judge without actual output.

this comes mainly down to how your application responds, perform a regular request to it and check the response to see what a good match would be.

Send String - if you dont want to add the hostname then drop that whole part, so like this:

GET /Sample/healthchecksimple HTTP/1.1\r\nConnection: Close\r\n\r\n

though formally this isn't allowed for a HTTP/1.1 request. it also depends on the way your application is setup, it might require a hostname or wont respond correctly without one.

best is to test this with curl or such from a system to see what happens with the different variants.