Getting Salesforce Data from External App

Salesforce encourages developers to authenticate using OAuth.

However, if you are creating a windows service to get data from SF, you'll need to choose the username/password flow.
https://ap1.salesforce.com/help/doc/en/remoteaccess_oauth_username_password_flow.htm

The Steps include:
1) Add new application via Setup -> Develop -> Remote Access
Under this method, the callback URL will not be used.

2) Perform a POST request
To get the authentication token:


https://login.salesforce.com/services/oauth2/token?grant_type=password&client_id=3MVG9lKcPoNINVBIPJjdw1J9LLM82Hn
FVVX19KY1uA5mu0QqEWhqKpoW3svG3XHrXDiCQjK1mdgAvhCscA9GE&client_secret=1955279925675241571&username=username@salesforceInstance.com&password=SFpassword

3) Parse return JSON and get access_token

{"id":"https://login.salesforce.com/id/00Dx0000000BV7z/005x00000012Q9P",
"issued_at":"1278448832702","instance_url":"https://na1.salesforce.com",
"signature":"0CmxinZir53Yex7nE0TD+zMpvIWYGb/bdJh6XfOH6EQ=","access_token":
"00Dx0000000BV7z!AR8AQAxo9UfVkh8AlV0Gomt9Czx9LjHnSSpwBMmbRcgKFmxOtvxjTrKW1
9ye6PE3Ds1eQz3z8jr3W7_VbWmEu4Q8TVGSTHxs"}

4) Perform a GET request

https://ap1.salesforce.com/services/data/v20.0/sobjects/Account/0019000000B8JxR?fields=AccountNumber,BillingPostalCode

User-Agent: Fiddler
Authorization: OAuth  access_token
Host: ap1.salesforce.com