A short script using the FreeNAS API to cycle the AFP service off and back on. Just replace your root password and hostname in the script.

cycle-afp.py

#!/usr/bin/env python

import requests, json, time

password='root_password'
host='freenas_hostname'

login = ('root', password)
headers = {'Content-Type': "application/json"}
url = 'http://'+host+'/api/v1.0/services/services/afp/'

result = requests.put(
    url,
    headers=headers,
    auth=login,
    data=json.dumps({'srv_enable': 'False'})
)

print result.json()
time.sleep(1)

result = requests.put(
    url,
    headers=headers,
    auth=login,
    data=json.dumps({'srv_enable': 'True'})
)

print result.json()