How to fix Common FIX Session Connection Issues? Solutions

FIX Protocol Session Connectivity
Hi guys, in this post I would like to share my experience with financial information exchange (FIX) Connections which is essential to set up FIX connectivity for trading purposes. Financial information exchange (FIX) Connections are used in both Client Connectivity and Exchange connectivity space (in case exchange supports financial information exchange (FIX) Protocol or you are connecting to any broker via FIX  Protocol).

So whenever a new client comes onboard a new Fix Session will be needed for him who will be identified by the host, port, and comp ids like SenderCompID and TargetCompID.

Before you set up a new financial information exchange (FIX) session in your fix engine you will need to require network connectivity between the client's network and your network, this is usually done by the network team, and for security reasons, some firewall rules also need to be setup.

While working on this part you may face several network connectivity issues based on what are you choosing e.g. Radianz, VPN or internet.


Once the network connection gets established you are ready to connect to the client. Now client will send logon request (MessagType=A) with sequence no 1, 1 (At start of day) and with SenderCompID and TargetCompID agreed upon. 

On the TCP layer, first of all, socket connection gets established in the client IP and your IP and your Fix Engine listens on the port specified. once your Fix Engine gets logon request its validates the content and authenticity of the client and if all is OK it replies with another logon request message. 

Now your financial information exchange (FIX) session is established and you are ready to send orders via this connection.

Some important points to remember while troubleshooting FIX  connectivity issues:

1.Which FIX  Protocol versions are you using for connectivity? Both counterparties must use the same version of the FIX Protocol to establish FIX Connectivity.


2. Are you sending Correct SenderCompID (FIX Tag 49) and TargetCompID (FIX tag 50)? CompIDs must be configured on FIX Acceptor side.


3. Are you using the correct IP and Port?


4. Does your FIX Engine is sending the correct sequence number which brokers FIX Engine is expecting?


5.  Are you handling Resend requests correctly?



 If you like this article, You may also enjoy my other posts on FIX Protocol and Electronic trading:

• Top 20 FIX Protocol Interview Questions
• FIX Protocol Tutorial for beginners
• FIX Protocol Session or Admin messages tutorial
• Fix Session is not connecting how to diagnose it?
• Basics of FIX Protocol and FIX Engine
• Repeating groups in FIX
• Replaying messages in FIX protocol
• Difference between Session Level and Business message Reject
• Difference between FIX 4.2 vs FIX 4.4
• Writing your own FIX Engine