JSON Schema validating ip-address is not working

Question 1

Got it, it's not because Draft3Validator doesn't support "format/ip-address", but "oneOf", "allOf", "anyOf" and "not". So the API.json should be:

{
"$schema": "http://json-schema.org/draft-03/schema#",
"title": "test",
"type": "object",
"properties": {
    "type": {"enum": ["spice", "vnc"]},
    "listen": {
        "type": "string",
        "format": "ip-address"
    }
},   
"additionalProperties": false
}

See http://json-schema.org/draft-03/schema# and http://json-schema.org/draft-04/schema#

Question 2

Check out the docs

Format validation is optional, you need a format checker to enable it.

Question 3

The other thing I have noticed if you are using draft 4 (http://json-schema.org/draft-04/schema#) is it wants

"format": "ip-address"

to do its validation if you give it

"format": "ipv4"

..it does not validate at all.

Question 4

The correct way to use format checker is mentioned in the document.[Julian has already mentioned that]

from jsonschema import Draft3Validator, ValidationError, draft3_format_checker

my_schema = {
"$schema": "http://json-schema.org/draft-03/schema#",
"title": "test",
  "type": "object",
  "properties": {
    "listen": {
        "type": "string",
        "format": 'ip-address'
    },
    "type": {"enum": ["spice", "vnc"]}
},
"additionalProperties": False
}

if __name__ == '__main__':
    graphics1 = {'type': 'spice', 'listen': 'def'}
    graphics2 = {'type': 'vnc', 'listen': '127.0.0.1'}

    validator = Draft3Validator(my_schema, format_checker=draft3_format_checker)
    for x in range(1, 3):
        try:
            graphics = locals().get('graphics'+str(x))
            validator.validate(graphics)
        except ValidationError:
            print('; '.join(e.message for e in validator.iter_errors(graphics)))

Output:

'def' is not a 'ip-address'

Next when you are using format you can just use format keyword I mean without type keyword. source look at example in this doc and format section of this doc,

my_schema = {
"$schema": "http://json-schema.org/draft-03/schema#",
"title": "test",
  "type": "object",
  "properties": {
    "listen": {
        "format": 'ip-address'
    },
    "type": {"enum": ["spice", "vnc"]}
},
"additionalProperties": False
}

From your question it looks like you are trying to check both IPv4 and IPv6 but if you go with schema format: 'ip-address only IPv4 are validated.

from jsonschema import Draft3Validator, ValidationError, draft3_format_checker

my_schema = {
"$schema": "http://json-schema.org/draft-03/schema#",
"title": "test",
  "type": "object",
  "properties": {
    "listen": {
        "format": 'ip-address'
    },
    "type": {"enum": ["spice", "vnc"]}
},
"additionalProperties": False
}

if __name__ == '__main__':
    graphics1 = {'type': 'spice', 'listen': 'def'}
    graphics2 = {'type': 'vnc', 'listen': '127.0.0.1'}
    graphics3 = {'type': 'vnc', 'listen': '::1'}  # IPV6 localhost

    validator = Draft3Validator(my_schema, format_checker=draft3_format_checker)
    for x in range(1, 4):
        try:
            graphics = locals().get('graphics'+str(x))
            validator.validate(graphics)
        except ValidationError:
            print('; '.join(e.message for e in validator.iter_errors(graphics)))

Output:

'def' is not a 'ip-address'
'::1' is not a 'ip-address'

Now if you want to check both IPv4 and IPv6 with Draft7(Since the question is old and Draft7 its new have many other options as well). Here is the revised code with handles both IPv4/v6, error.

from jsonschema import draft7_format_checker, Draft7Validator

my_schema = {
"$schema": "http://json-schema.org/draft-07/schema#",
"title": "test",
  "type": "object",
  "properties": {
    "listen": {
        'oneOf': [
                    {"format": 'ipv4'},
                    {"format": 'ipv6'},
                ],
    },
    "type": {"enum": ["spice", "vnc"]}
},
"additionalProperties": False
}

if __name__ == '__main__':
    test_list = [{'type': 'spice', 'listen': 'def'}, {'type': 'vnc', 'listen': '127.0.0.1'},{'type': 'vnc', 'listen': '::1'}]

    validator = Draft7Validator(my_schema, format_checker=draft7_format_checker)
    for my_json in test_list:
        errors = validator.iter_errors(my_json)
        for i, error in enumerate(errors):
            print(error.message)

        # # If you want to see more detail cause of each error use this
        # # the ValidationError.context attribute can be used to see the sub-errors which caused the failure
        # for i, error in enumerate(errors):
        #     for suberror in sorted(error.context, key=lambda e: e.schema_path):
        #         print(list(suberror.relative_schema_path), suberror.message, sep=", ")

Output:

'def' is not valid under any of the given schemas

and sample output of detail output(which is commented in above snippet)

[0, 'format'], 'def' is not a 'ipv4'
[1, 'format'], 'def' is not a 'ipv6'

error.context : If the error was caused by errors in subschemas, the list of errors from the subschemas will be available on this property. The schema_path and path of these errors will be relative to the parent error. Reference: https://python-jsonschema.readthedocs.io/en/stable/errors/