PJSIP学习笔记——从simple_pjsua.c示例程序了解PJSUA-LIB的基本使用流程

要了解pjsip的使用，simple_pjsua.c是一个很好的例子，虽然代码只有短短的172行，却展示了pjsua-lib层的完整使用流程、注册流程和基本呼叫流程。
下面是学习过程中整理的simple_pjsua.c中的main函数主要流程：



先来看看pjsip-apps/src/samples/simple_pjsua.c的main函数

/*
 * main()
 *
 * argv[1] may contain URL to call.
 */
int main(int argc, char *argv[])
{
    pjsua_acc_id acc_id;
    pj_status_t status;

//  创建PJSIP
    /* Create pjsua first! */
    status = pjsua_create();
    if (status != PJ_SUCCESS) error_exit("Error in pjsua_create()", status);

//  校验被叫SIP地址是否正确
    /* If argument is specified, it's got to be a valid SIP URL */
    if (argc > 1) {
	status = pjsua_verify_url(argv[1]);
	if (status != PJ_SUCCESS) error_exit("Invalid URL in argv", status);
    }

//    初始化PJSUA，设置回调函数
    /* Init pjsua */
    {
	pjsua_config cfg;
	pjsua_logging_config log_cfg;

	pjsua_config_default(&cfg);
	cfg.cb.on_incoming_call = &on_incoming_call;
	cfg.cb.on_call_media_state = &on_call_media_state;
	cfg.cb.on_call_state = &on_call_state;

	pjsua_logging_config_default(&log_cfg);
	log_cfg.console_level = 4;

	status = pjsua_init(&cfg, &log_cfg, NULL);
	if (status != PJ_SUCCESS) error_exit("Error in pjsua_init()", status);
    }

//    创建PJSIP的传输端口
    /* Add UDP transport. */
    {
	pjsua_transport_config cfg;

	pjsua_transport_config_default(&cfg);
	cfg.port = 5060;
	status = pjsua_transport_create(PJSIP_TRANSPORT_UDP, &cfg, NULL);
	if (status != PJ_SUCCESS) error_exit("Error creating transport", status);
    }

//    启动PJSIP
    /* Initialization is done, now start pjsua */
    status = pjsua_start();
    if (status != PJ_SUCCESS) error_exit("Error starting pjsua", status);

//    设置SIP用户帐号
    /* 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);
    }

//    发起一个呼叫
    /* If URL is specified, make call to the URL. */
    if (argc > 1) {
	pj_str_t uri = pj_str(argv[1]);
	status = pjsua_call_make_call(acc_id, &uri, 0, NULL, NULL, NULL);
	if (status != PJ_SUCCESS) error_exit("Error making call", status);
    }

//    循环等待
    /* Wait until user press "q" to quit. */
    for (;;) {
	char option[10];

	puts("Press 'h' to hangup all calls, 'q' to quit");
	if (fgets(option, sizeof(option), stdin) == NULL) {
	    puts("EOF while reading stdin, will quit now..");
	    break;
	}

	if (option[0] == 'q')
	    break;

	if (option[0] == 'h')
	    pjsua_call_hangup_all();
    }

    /* Destroy pjsua */
    pjsua_destroy();

    return 0;
}

来电的回调函数

//来电回调函数
/* Callback called by the library upon receiving incoming call */
static void on_incoming_call(pjsua_acc_id acc_id, pjsua_call_id call_id,
			     pjsip_rx_data *rdata)
{
    pjsua_call_info ci;

    PJ_UNUSED_ARG(acc_id);
    PJ_UNUSED_ARG(rdata);

//    获得呼叫信息
    pjsua_call_get_info(call_id, &ci);

    PJ_LOG(3,(THIS_FILE, "Incoming call from %.*s!!",
			 (int)ci.remote_info.slen,
			 ci.remote_info.ptr));

//    自动应答呼叫
    /* Automatically answer incoming calls with 200/OK */
    pjsua_call_answer(call_id, 200, NULL, NULL);
}

呼叫状态改变的回调函数，没有做实质性的操作：

//呼叫状态改变的回调函数
/* Callback called by the library when call's state has changed */
static void on_call_state(pjsua_call_id call_id, pjsip_event *e)
{
    pjsua_call_info ci;

    PJ_UNUSED_ARG(e);

    pjsua_call_get_info(call_id, &ci);
    PJ_LOG(3,(THIS_FILE, "Call %d state=%.*s", call_id,
			 (int)ci.state_text.slen,
			 ci.state_text.ptr));
}

媒体状态改变的回调函数：

//媒体状态改变的回调函数
/* Callback called by the library when call's media state has changed */
static void on_call_media_state(pjsua_call_id call_id)
{
    pjsua_call_info ci;

    pjsua_call_get_info(call_id, &ci);

//    当媒体为激活时，连接呼叫和声音设备
    if (ci.media_status == PJSUA_CALL_MEDIA_ACTIVE) {
	// When media is active, connect call to sound device.
	pjsua_conf_connect(ci.conf_slot, 0);
	pjsua_conf_connect(0, ci.conf_slot);
    }
}