[php] "Adaptive Server is unavailable or does not exist" error connecting to SQL Server from PHP

I'm attempting to connect to a SQL Server 2005 DB from my Mac using unixODBC and FreeTDS as I have outlined here. However, when I try to connect in to a different DB using the same setup, I get:

Connection Failed:[FreeTDS][SQL Server]Unable to connect: Adaptive Server is unavailable or does not exist.

Here is my freetds.conf setup:

[my_db]
host = 12.34.56.789
port = 1433
tds version = 8.0

And here is my odbc.ini:

[my_dsn]
Driver = /opt/local/lib/libtdsodbc.so
Description = My Database
Trace = no
Servername = my_db
Database = MyDB

[ODBC Data Sources]
my_dsn = FreeTDS

I am still able to connect to the other DB I set up on this computer (described in my blog post linked above), so I'm pretty sure that the error isn't on the Mac end. I've verified on the server that I'm using the correct IP address and port. Any thoughts on what could be the problem, and if it's on the server end?

Responding because this answer came up first for search when I was having the same issue:

[08S01][unixODBC][FreeTDS][SQL Server]Unable to connect: Adaptive Server is unavailable or does not exist

MSSQL named instances have to be configured properly without setting the port. (documentation on the freetds config says set instance or port NOT BOTH)

freetds.conf

[Name]
host = Server.com
instance = instance_name
#port = port is found automatically, don't define explicitly
tds version = 8.0
client charset = UTF-8

And in odbc.ini just because you can set Port, DON'T when you are using a named instance.

1. See information about the SQL server

tsql -LH SERVER_IP_ADDRESS

locale is "C"
locale charset is "646"
ServerName TITAN
InstanceName MSSQLSERVER
IsClustered No
Version 8.00.194
tcp 1433
np \\TITAN\pipe\sql\query

2. Set your freetds.conf

tsql -C    
freetds.conf directory: /usr/local/etc

[TITAN]
host = SERVER_IP_ADDRESS
port = 1433
tds version = 7.2

3 Try

tsql -S TITAN -U user -P password

OR

 'dsn' => 'dblib:host=TITAN:1433;dbname=YOURDBNAME',

See also http://www.freetds.org/userguide/confirminstall.htm (Example 3-5.)

If you get message 20009, remember you haven't connected to the machine. It's a configuration or network issue, not a protocol failure. Verify the server is up, has the name and IP address FreeTDS is using, and is listening to the configured port.

After countless hours of frustration I managed to get all working:

odbcinst.ini:

[FreeTDS]
Description = FreeTDS Driver v0.91
Driver = /usr/lib/x86_64-linux-gnu/odbc/libtdsodbc.so
Setup = /usr/lib/x86_64-linux-gnu/odbc/libtdsS.so
fileusage=1
dontdlclose=1
UsageCount=1

odbc.ini:

[test]
Driver = FreeTDS
Description = My Test Server
Trace = No
#TraceFile = /tmp/sql.log
ServerName = mssql
#Port = 1433
instance = SQLEXPRESS
Database = usedbname
TDS_Version = 4.2

FreeTDS.conf:

[mssql]
host = hostnameOrIP
instance = SQLEXPRESS
#Port = 1433
tds version = 4.2

First test connection (mssql is a section name from freetds.conf):

tsql -S mssql -U username -P password

You must see some settings but no errors and only a 1> prompt. Use quit to exit.

Then let's test DSN/FreeTDS (test is a section name from odbc.ini; -v means verbose):

isql -v test username password -v

You must see message Connected!

I've found an issue happen to be with the Firewall. So, make sure your IP is whitelisted and the firewall does not block your connection. You can check connectivity with:

tsql -H somehost.com -p 1433

In my case, the output was:

Error 20009 (severity 9):
  Unable to connect: Adaptive Server is unavailable or does not exist
  OS error 111, "Connection refused"
There was a problem connecting to the server

I had the same issue, my problem was that the firewall on the server wasn't open from the current ip address.

Bud, disable selinux or add the following to your RedHat/CentOS Server:

setsebool -P httpd_can_network_connect_db 1
setsebool -P httpd_can_network_connect 1

Best always!

It sounds like you have a problem with your dsn or odbc data source.

Try bypassing the dsn first and connect using:

TDSVER=8.0 tsql -S *serverIPAddress* -U *username* -P *password*

If that works, you know its an issue with your dsn or with freetds using your dsn. Also, it is possible that your tds version is not compatible with your server. You might want to try other TDSVER settings (5.0, 7.0, 7.1).

Try changing server name to "localhost"

pymssql.connect(server="localhost", user="myusername", password="mypwd", database="temp",port="1433")