Error in rJava::.jcall(driver@jdrv, "Ljava/sql/Connection;", "connect", : java.sql.SQLException: Network error IOException: Connection refused: connect

Error in rJava::.jcall(driver@jdrv, "Ljava/sql/Connection;", "connect", :
 
java.sql.SQLException: Network error IOException: Connection refused: connect
 
Why do I get java.sql.SQLException: "Network error IOException: Connection refused: connect" when trying to get a connection?
 
The "Connection refused" exception is thrown by jTDS when it is unable to connect to the server. There may be a number of reasons why this could happen:
The server name is misspelled or the port number is incorrect.
SQL Server is not configured to use TCP/IP. Either enable TCP/IP from SQL Server's Network Utility app or have jTDS connect via named pipes (see the URL format for information on how to do this).
There is a firewall blocking port 1433 on the server.
 

To check whether TCP/IP is enabled and the port is not blocked you can use "telnet <server_host> 1433". Until telnet doesn't connect, jTDS won't either. If you can't figure out why ask your network administrator for help.