Alejandro, first thanks to you for respond me, I'm using the example simple_pjsua that is included in the pjproject-1.6 that I downloaded from like I already told you, and I have a server using Asterisk, when I try to connect to the server whit a softphone it is successful, I call from a pc to another and also with a webcam I can watch the other person, but when I run the example it doesn't connect, and I do not know to fix the problem, I have tried some configurations in the Asterisk server and in my SIP client and nothing. I'm sending you the configuration in the Asterisk server, I think that like you told me, there are no the main configurations. The asterisk server: [2003] type = friend username= 2003 fromuser=2003 language = es context= prueba host= dynamic secret=2003 The part of the code that is assigned to the connection is the following: /* Register to SIP server by creating SIP account. */ { pjsua_acc_config cfg; pjsua_acc_config_default(&cfg); cfg.id = pj_str("sip:" SIP_USER "@" SIP_DOMAIN); cfg.reg_uri = pj_str("sip:" SIP_DOMAIN); cfg.cred_count = 1; cfg.cred_info[0].realm = pj_str(SIP_DOMAIN); cfg.cred_info[0].scheme = pj_str("Digest"); cfg.cred_info[0].username = pj_str(SIP_USER); cfg.cred_info[0].data_type = PJSIP_CRED_DATA_PLAIN_PASSWD; cfg.cred_info[0].data = pj_str(SIP_PASSWD); status = pjsua_acc_add(&cfg, PJ_TRUE, &acc_id); if (status != PJ_SUCCESS) error_exit("Error adding account", status); } You need the following definition to understand the parameters #define SIP_DOMAIN "10.12.165.11" /*the server IP*/ #define SIP_USER "2003" /*The number to register in asterisk*/ #define SIP_PASSWD "2003" Tell me what I'm missing in the Server on in the example... Thanks a lot.