If I can ping my DB server, is my SQL Server connection guaranteed to work? I am using a default connection string in my code. My program runs fine locally but overseas sites are having issues and I am wondering if SQL might be using a TCP or UDP port that is still blocked.
Here is the connection string "Data Source=xxxx.xxxx.com; Initial Catalog = xxxxx; User ID=xxxxx;password=xxxxx"
No. The SQL Server Service must at least be running on the server for any mssql connections to work. The server itself can be up - running and pingable without the SQL Server Serice running.
As far as I understand your question you are asking whether ICMP "ping" packet which returns guarantees you can open a connection on a particular TCP port? The answer is NO. It is also not the other way around - "ping" packets might be blocked by a firewall.
You might also need to check whether the TCP/IP protocol is enabled using SQL Server Configuration Manager. Even when MSSQLSvc is running, it might not respond to remote requests.