org.postgresql.util.PSQLException: Protocol error. Session setup failed

I am trying to connect to PostgreSQL database on my local system.

The code is:

Class.forName("org.postgresql.Driver");
String url = "jdbc:postgresql://localhost:5432/postgres?user=postgres&password=major";
Connection conn = DriverManager.getConnection(url);

Running the code I get:

org.postgresql.util.PSQLException: Protocol error. Session setup failed.

Using postgresql-8.4-701.jdbc3 on PostgreSql 8.4