<html><head></head><body><div style="font-family:Helvetica Neue, Helvetica, Arial, sans-serif;font-size:13px;"><div>Hi,</div><div><br></div><div>OpenSSL version is 1.1.0e.</div><div><br></div><div>I am writing high-performance DTLS server which can accept thousands of connections concurrently. </div><div><br></div><div>Originally, I decided, DTLSv1_listen would be called inside the listener thread, once <span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;">DTLSv1_listen returns 1 i.e. successful, a new async socket will be created, it will be bound (using bind) and connected (using BIO_connect) with <span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;">DTLSv1_listen returned address. </span></span></div><div><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;">This new socket will be passed to service thread, BIO_set_fd will set this fd and SSL_accept will be called from service thread to complete the remaining handshake and data exchange etc.</span></span></div><div><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><br></span></span></div><div><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;">But behavior is not same as above, I have to call <span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;">SSL_accept after bind and connect inside the listen, where DTLS handshake is completed. If SSL_accept is not called then <span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;">DTLSv1_listen is continuously called and always return 1 in listener thread. </span></span></span></span></div><div><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><br></span></span></span></span></div><div><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;">Could you please guide to resolve this issue or how to write multi-threaded dtls server where connection acceptance can be done inside the listener thread using <span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;">DTLSv1_listen?</span></span></span></span></span></div><div><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><br></span></span></span></span></span></div><div><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;">Thanks in Advance,</span></span></span></span></span></div><div><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;">Anand</span></span></span></span></span></div><div><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><span style="color: rgb(0, 0, 0); font-family: "Helvetica Neue", Helvetica, Arial, sans-serif;"><br></span></span></div></div></body></html>