Error "25507 The specified service name or protocol is unknown." when trying to access a remote database via TCP/IP protocol.

Resolving The Problem

• It is a common mistake to set the TCP/IP protocol in local client machine's sqlhosts exactly as it appears on the sqlhosts file that belongs to the remote instance you want to connect to. If the local machine supports a different implementation of TCP/IP protocol (ex: HP-UX uses sockets), than the remote server machine, (ex: Solaris uses TLI), but the local machine is set the same as the remote machine (the HP-UX machine is set to use TLI instead of sockets), this error arises at connection time.
  
  The TCP/IP settings are machine based. Set the use of TLI or SOC to match the TCP/IP protocol that is supported by the operating system where the local sqlhosts resides. The correct settings for your local installation are documented in the Machine Notes of the IBM Informix product. Here are some examples of operating systems and the TCP/IP protocols they use:
  
  

This operating system	Uses this type of TCP protocol
Solaris (IDS 11.10 and above)	soc/tli
Solaris (IDS before 11.10)	tli
AIX	soc
HP UX	soc
Windows (all platforms)	soc
Tru64	soc
Linux	soc


Example:

Assume there is an instance called online1 on a HP-UX machine named test1, and you have another instance called online2 on a Solaris machine named test2.

You want to be able to connect to online1 from online2 and vice versa. The sqlhosts files must look like these:

On test1 (HP-UX that uses soc):
#Server Name     Protocol    Hostname    Service Name
online1          onsoctcp    test1       online1
online2          onsoctcp    test2       online2

On test2 (Solaris that uses tli):
#Server Name     Protocol    Hostname    Service Name
online1          ontlitcp    test1       online1
online2          ontlitcp    test2       online2

• Check the /etc/services file. Make sure that there is an entry that corresponds to the service name entry in the sqlhosts file.
  
  Example:
  
  #Service Name     Port/Protocol
  online1           1525/tcp
  online2           1526/tcp