[java] JDBC connection failed, error: TCP/IP connection to host failed

I want to connect Java class file with SQL server 2012. I have logged in with SQL server authentication. But i am receiving error in connectivity.

ERROR: The TCP/IP connection to the host 127.0.0.1, port 1433 has failed. Error: "Connection refused: connect. Verify the connection properties. Make sure that an instance of SQL Server is running on the host and accepting TCP/IP connections at the port. Make sure that TCP connections to the port are not blocked by a firewall.".

My code ---

Class.forName("com.microsoft.sqlserver.jdbc.SQLServerDriver");  //1. Register your driver
//2. get the connection object
//Connection con = DriverManager.getConnection("jdbc:sqlserver://localhost;databaseName=aysha","sa","admin");
Connection con = DriverManager.getConnection("jdbc:sqlserver://127.0.0.1;databaseName=aysha","user=sa","password=admin");
 //"jdbc:sqlserver://127.0.0.1:1433; Instance=SQL2008;" +       "databaseName=MB;user=sa;password=123;";
//Connection con = DriverManager.getConnection("jdbc:sqlserver://localhost:1433;databaseName=aysha","sa" , "password");
//3. Prepare a statement
Statement stmt = con.createStatement();
//4. Write the query`
String sql = "Select * from employee";
//5. Execute the statement and 
ResultSet rs = stmt.executeQuery(sql);
//6. Process the result set

while (rs.next())
{
    System.out.println(rs.getInt(1));
}

Easy Solution

Got to Start->All Programs-> Microsoft SQL Server 2012-> Configuration Tool -> Click SQL Server Configuration Manager ->Expand SQL Server Network Configuration-> Protocol ->Enable TCP/IP Right box

Double Click on TCP/IP and go to IP Adresses Tap and Put port 1433 under TCP port.

Go to Start->All Programs-> Microsoft SQL Server 2012-> Configuration Tool -> Click SQL Server Configuration Manager.

If you see that SQL Server/ SQL Server Browser State is 'stopped'.Right click on SQL Server/SQL Server Browser and click start. In some cases above state can stop though TCP connection to port 1433 is assigned.

1. Open SQL Server Configuration Manager, and then expand SQL Server 2012 Network Configuration.
2. Click Protocols for InstanceName, and then make sure TCP/IP is enabled in the right panel and double-click TCP/IP.
3. On the Protocol tab, notice the value of the Listen All item.
4. Click the IP Addresses tab: If the value of Listen All is yes, the TCP/IP port number for this instance of SQL Server 2012 is the value of the TCP Dynamic Ports item under IPAll. If the value of Listen All is no, the TCP/IP port number for this instance of SQL Server 2012 is the value of the TCP Dynamic Ports item for a specific IP address.
5. Make sure the TCP Port is 1433.
6. Click OK.

If there are any more questions, please let me know.

Thanks.

If you are using a named instance, the port you using likely is 1434, instead of 1433, so please check that out using telnet or netstat aforementioned too.

The error is self explanatory:

• Check if your SQL server is actually up and running
• Check SQL server hostname, username and password is correct
• Check there's no firewall rule blocking TCP connection to port 1433
• Check the host is actually reachable

A good check I often use is to use telnet, eg on a windows command prompt run:

telnet 127.0.0.1 1433

If you get a blank screen it indicates network connection established successfully, and it's not a network problem. If you get 'Could not open connection to the host' then this is network problem

important:
after any changes or new settings you must restart SQLSERVER service. run services.msc on Windows

Open %windir%\System32 folder and find SQLServerManagerXX.msc

For example:

C:\Windows\System32\SQLServerManager14.msc

Go to protocols settings then enable TCP/IP port is 1433 by default

As the error says, you need to make sure that your sql server is running and listening on port 1433. If server is running then you need to check whether there is some firewall rule rejecting the connection on port 1433.

Here are the commands that can be useful to troubleshoot:

1. Use netstat -a to check whether sql server is listening on the desired port
2. As gerrytan mentioned in answer, you can try to do the telnet on the host and port