In our universal AAA (Authentication, Authorization, and Accounting) infrastructure project, we have already developed the implementations of Diameter Base Protocol and Diameter EAP Application. As part of this project, we developed the first open-source of an EAP-TTLS server on Diameter EAP Application for network access control. EAP-TTLS is one of the authentication methods in EAP. EAP-TTLS has two phases. In phase 1, the user authenticates the EAP-TTLS server by the certificate of the EAP-TTLS server. In phase 2, the EAP-TTLS server authenticates the user by user's password transmitted through the secure tunnel established in phase 1. Our implementation supports several authentication methods in phase 2 such as PAP, CHAP, MS-CHAP, and MS-CHAPv2. It was made sure that the EAP-TTLS server worked correctly for several types of user terminals such as Windows, Linux, iPad, and Android. The evaluation results show that the processing time of the EAP-TTLS server is short enough for practical use.