[squid-users] test ICAP server

[Robin Wood]

Hi
I want to write my own ICAP server, but all the sample code I've found is
failing, the majority with this error from squidclient:

squidclient -h 192.168.0.7 -p 1344 icap://192.168.0.7:1344/request_mod
ICAP/1.0 400 Bad Request

And this error when accessed through Squid itself:

ICAP protocol error.

The system returned: [No Error]

This means that some aspect of the ICAP communication failed.

I've got this in my squid.conf:

# Enable ICAP for request and response modification
icap_enable on
icap_service service_req reqmod_precache icap://192.168.0.7:1344/request_mod
icap_service service_resp respmod_precache icap://
192.168.0.7:1344/response_mod

# ICAP adaptation rules
adaptation_access service_req allow all
adaptation_access service_resp allow all

And I've tried running both Python and Ruby servers taken from various
places. A lot are logging that they've received and replied to requests:

Received request: OPTIONS icap://192.168.0.7:1344/request_mod ICAP/1.0
Responded to OPTIONS request

The servers are all listening, I've checked that:

$ ss -antp | grep 1344
LISTEN     0      4096                       0.0.0.0:1344
 0.0.0.0:*     users:(("ruby",pid=563029,fd=5))

The closest I've got is this one:

https://gist.github.com/digininja/a98b3567e0aeb218d37cdd337bb12f34

It seems to be working as it sees the headers and says it has returned data:

Received request: REQMOD icap://192.168.0.7:1344/request_mod ICAP/1.0
Original Headers:
Host: 192.168.0.7:1344
Date: Fri, 07 Feb 2025 10:10:30 GMT
Encapsulated: req-hdr=0, null-body=91
Preview: 0
Allow: 204, trailers
Modified request sent back

But I still get errors.

What could be wrong?

Does someone have some example server code they know works that I can test
to help debug it?

Robin
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