ThingWorx Edge C SDK > Using SSL/TLS for Security > Troubleshooting Connection Errors (C SDK v.1.4.0 and earlier)
  
Troubleshooting Connection Errors (C SDK v.1.4.0 and earlier)
If your Edge application uses an earlier version of the C SDK than 1.4.0 and it cannot establish a secure (SSL/TLS) websocket Connection using the C SDK, you may see one of the following errors:
Error initializing SSL connection
twWs_Connect: Error restarting socket. Error 0.
These errors are known to occur after the version of Tomcat used for ThingWorx platform has been upgraded to 8.0.35 or higher and versions of the C SDK earlier than 1.4.0 are in use in the application. The later versions of Tomcat have disabled RSA-based ciphers by default due to forward secrecy concerns. The ciphers supported by the axTLS libraries earlier than v.2.1.2.1 (the version in the C SDK 1.4.0) are disabled by default by this change to Tomcat. When a C SDK device tries to connect, an error “No compatible ciphers” is returned.
It is strongly recommended that you upgrade to the latest version of the C SDK and use the OpenSSL library provided in the distribution bundle. You then will need to rebuild your application. As of release 2.2.1, the axTLS libraries are no longer provided in the distribution bundle.