Sample code below is based on ESP8266_NONOS_SDK.

ESP8266 init with station mode，then it can scan routers nearby.

Notice that call

/******************************************************************************
 * FunctionName : scan_done
 * Description  : scan done callback
 * Parameters   :  arg: contain the aps information; 
                          status: scan over status
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
scan_done(void *arg, STATUS status)
{
  uint8 ssid[33];
  char temp[128];
 
  if (status == OK)
  {
    struct bss_info *bss_link = (struct bss_info *)arg;
 
    while (bss_link != NULL)
    {
      os_memset(ssid, 0, 33);
      if (os_strlen(bss_link->ssid) <= 32)
      {
        os_memcpy(ssid, bss_link->ssid, os_strlen(bss_link->ssid));
      }
      else
      {
        os_memcpy(ssid, bss_link->ssid, 32);
      }
      os_printf("(%d,\"%s\",%d,\""MACSTR"\",%d)\r\n",
                 bss_link->authmode, ssid, bss_link->rssi,
                 MAC2STR(bss_link->bssid),bss_link->channel);
      bss_link = bss_link->next.stqe_next;
    }
  }
  else
  {
     os_printf("Scan failed!\r\n");
  }
 
}
 
/******************************************************************************
 * FunctionName : user_scan
 * Description  : wifi scan, only can be called after system init done.
 * Parameters   :  none
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_scan(void)
{
   if(wifi_get_opmode() == SOFTAP_MODE)
   {
     os_printf("SoftAP mode is enabled. Enable station mode to scan...\r\n");
     return;
   }
   wifi_station_scan(NULL,scan_done);
 
}
 
 
/******************************************************************************
 * FunctionName : user_init
 * Description  : entry of user application, init user function here
 * Parameters   : none
 * Returns      : none
*******************************************************************************/
void user_init(void)
{
    os_printf("SDK version:%s\n", system_get_sdk_version());
    
   //Set softAP + station mode 
   wifi_set_opmode(STATIONAP_MODE); 
 
   // wifi scan has to after system init done.
   system_init_done_cb(user_scan);
 
}

If you want to scan a specific AP，for example，scan an AP of which SSID is “ESP8266”. You only need to set the value of parameter "SSID" in structure "scan_config" when calling wifi_station_scan. 

void ICACHE_FLASH_ATTR
user_scan(void)
{
   if(wifi_get_opmode() == SOFTAP_MODE)
   {
     os_printf("ap mode can't scan !!!\r\n");
     return;
   }
   struct scan_config config;

   os_memset(&config, 0, sizeof(config));

   config.ssid = "ESP8266";
   
   wifi_station_scan(&config,scan_done);

}

Sample code below is based on ESP8266 SDK without OS.

1. Start from user_init

2. Connect to router

3. Connect to cn.bing.com as example

4. Send some HTTP packet..

Note: for ESP8266_RTOS_SDK, please call espconn_init() in the user_init to initialize espconn first.

#include "espconn.h"
#include "mem.h"
 
#define NET_DOMAIN "cn.bing.com"
#define pheadbuffer "GET / HTTP/1.1\r\nUser-Agent: curl/7.37.0\r\nHost: %s\r\nAccept: */*\r\n\r\n"
 
#define packet_size   (2 * 1024)
 
LOCAL os_timer_t test_timer;
LOCAL struct espconn user_tcp_conn;
LOCAL struct _esp_tcp user_tcp;
ip_addr_t tcp_server_ip;
 
 
/******************************************************************************
 * FunctionName : user_tcp_recv_cb
 * Description  : receive callback.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_tcp_recv_cb(void *arg, char *pusrdata, unsigned short length)
{
   //received some data from tcp connection
    
    os_printf("Received data string: %s \r\n", pusrdata);
    
}
/******************************************************************************
 * FunctionName : user_tcp_sent_cb
 * Description  : data sent callback.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_tcp_sent_cb(void *arg)
{
   //data sent successfully
 
    os_printf("Sent callback: data sent successfully.\r\n");
}
/******************************************************************************
 * FunctionName : user_tcp_discon_cb
 * Description  : disconnect callback.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_tcp_discon_cb(void *arg)
{
   //tcp disconnect successfully
    
    os_printf("Disconnected from server.\r\n");
}
/******************************************************************************
 * FunctionName : user_esp_platform_sent
 * Description  : Processing the application data and sending it to the host
 * Parameters   : pespconn -- the espconn used to connetion with the host
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_send_data(struct espconn *pespconn)
{
    char *pbuf = (char *)os_zalloc(packet_size);
 
    os_sprintf(pbuf, pheadbuffer, NET_DOMAIN);
 
   espconn_send(pespconn, pbuf, os_strlen(pbuf));
    
   os_free(pbuf);
 
}
 
/******************************************************************************
 * FunctionName : user_tcp_connect_cb
 * Description  : A new incoming tcp connection has been connected.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_tcp_connect_cb(void *arg)
{
    struct espconn *pespconn = arg;
 
    os_printf("Connected to server...\r\n");
 
    espconn_regist_recvcb(pespconn, user_tcp_recv_cb);
    espconn_regist_sentcb(pespconn, user_tcp_sent_cb);
    espconn_regist_disconcb(pespconn, user_tcp_discon_cb);
    
    user_send_data(pespconn);
}
 
/******************************************************************************
 * FunctionName : user_tcp_recon_cb
 * Description  : reconnect callback, error occured in TCP connection.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_tcp_recon_cb(void *arg, sint8 err)
{
   //error occured , tcp connection broke. user can try to reconnect here. 
    
    os_printf("Reconnect callback called, error code: %d !!! \r\n",err);
}
 
#ifdef DNS_ENABLE
/******************************************************************************
 * FunctionName : user_dns_found
 * Description  : dns found callback
 * Parameters   : name -- pointer to the name that was looked up.
 *                ipaddr -- pointer to an ip_addr_t containing the IP address of
 *                the hostname, or NULL if the name could not be found (or on any
 *                other error).
 *                callback_arg -- a user-specified callback argument passed to
 *                dns_gethostbyname
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_dns_found(const char *name, ip_addr_t *ipaddr, void *arg)
{
    struct espconn *pespconn = (struct espconn *)arg;
 
    if (ipaddr == NULL) 
   {
        os_printf("user_dns_found NULL \r\n");
        return;
    }
 
   //dns got ip
    os_printf("user_dns_found %d.%d.%d.%d \r\n",
            *((uint8 *)&ipaddr->addr), *((uint8 *)&ipaddr->addr + 1),
            *((uint8 *)&ipaddr->addr + 2), *((uint8 *)&ipaddr->addr + 3));
 
    if (tcp_server_ip.addr == 0 && ipaddr->addr != 0) 
   {
      // dns succeed, create tcp connection
        os_timer_disarm(&test_timer);
        tcp_server_ip.addr = ipaddr->addr;
        os_memcpy(pespconn->proto.tcp->remote_ip, &ipaddr->addr, 4); // remote ip of tcp server which get by dns
 
        pespconn->proto.tcp->remote_port = 80; // remote port of tcp server
       
        pespconn->proto.tcp->local_port = espconn_port(); //local port of ESP8266
 
        espconn_regist_connectcb(pespconn, user_tcp_connect_cb); // register connect callback
        espconn_regist_reconcb(pespconn, user_tcp_recon_cb); // register reconnect callback as error handler
 
        espconn_connect(pespconn); // tcp connect
    }
}
 
/******************************************************************************
 * FunctionName : user_esp_platform_dns_check_cb
 * Description  : 1s time callback to check dns found
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_dns_check_cb(void *arg)
{
    struct espconn *pespconn = arg;
 
    espconn_gethostbyname(pespconn, NET_DOMAIN, &tcp_server_ip, user_dns_found); // recall DNS function
 
    os_timer_arm(&test_timer, 1000, 0);
}
#endif
/******************************************************************************
 * FunctionName : user_check_ip
 * Description  : check whether get ip addr or not
 * Parameters   : none
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_check_ip(void)
{
    struct ip_info ipconfig;
 
   //disarm timer first
    os_timer_disarm(&test_timer);
 
   //get ip info of ESP8266 station
    wifi_get_ip_info(STATION_IF, &ipconfig);
 
    if (wifi_station_get_connect_status() == STATION_GOT_IP && ipconfig.ip.addr != 0) 
   {
      os_printf("Connected to router and assigned IP!\r\n");
 
      // Connect to tcp server as NET_DOMAIN
      user_tcp_conn.proto.tcp = &user_tcp;
      user_tcp_conn.type = ESPCONN_TCP;
      user_tcp_conn.state = ESPCONN_NONE;
       
#ifdef DNS_ENABLE
       tcp_server_ip.addr = 0;
       espconn_gethostbyname(&user_tcp_conn, NET_DOMAIN, &tcp_server_ip, user_dns_found); // DNS function
 
       os_timer_setfn(&test_timer, (os_timer_func_t *)user_dns_check_cb, &user_tcp_conn);
       os_timer_arm(&test_timer, 1000, 0);
#else
 
       const char esp_tcp_server_ip[4] = {X, X, X, X}; // remote IP of TCP server
 
       os_memcpy(user_tcp_conn.proto.tcp->remote_ip, esp_tcp_server_ip, 4);
 
       user_tcp_conn.proto.tcp->remote_port = XXXX;  // remote port
       
       user_tcp_conn.proto.tcp->local_port = espconn_port(); //local port of ESP8266
 
       espconn_regist_connectcb(&user_tcp_conn, user_tcp_connect_cb); // register connect callback
       espconn_regist_reconcb(&user_tcp_conn, user_tcp_recon_cb); // register reconnect callback as error handler
       espconn_connect(&user_tcp_conn); 
 
#endif
    } 
   else
   {
        
        if ((wifi_station_get_connect_status() == STATION_WRONG_PASSWORD ||
                wifi_station_get_connect_status() == STATION_NO_AP_FOUND ||
                wifi_station_get_connect_status() == STATION_CONNECT_FAIL)) 
        {
         os_printf("Connection to router failed!\r\n");
        } 
      else
      {
           //re-arm timer to check ip
            os_timer_setfn(&test_timer, (os_timer_func_t *)user_check_ip, NULL);
            os_timer_arm(&test_timer, 100, 0);
        }
    }
}
 
 
/******************************************************************************
 * FunctionName : user_set_station_config
 * Description  : set the router info which ESP8266 station will connect to 
 * Parameters   : none
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_set_station_config(void)
{
   // Wifi configuration 
   char ssid[32] = SSID; 
   char password[64] = PASSWORD; 
   struct station_config stationConf; 
    
   os_memset(stationConf.ssid, 0, 32);
   os_memset(stationConf.password, 0, 64);
    
   // No MAC-specific scanning
   stationConf.bssid_set = 0; 
    
   //Set ap settings 
   os_memcpy(&stationConf.ssid, ssid, 32); 
   os_memcpy(&stationConf.password, password, 64); 
   wifi_station_set_config(&stationConf); 
 
   // Set timer to check whether router allotted an IP 
   os_timer_disarm(&test_timer);
   os_timer_setfn(&test_timer, (os_timer_func_t *)user_check_ip, NULL);
   os_timer_arm(&test_timer, 100, 0);
 
}
 
 
/******************************************************************************
 * FunctionName : user_init
 * Description  : entry of user application, init user function here
 * Parameters   : none
 * Returns      : none
*******************************************************************************/
void user_init(void)
{
   os_printf("SDK version:%s\n", system_get_sdk_version());
    
   //Set softAP + station mode 
   wifi_set_opmode(STATIONAP_MODE); 
 
   //ESP8266 connect to router
   user_set_station_config();
 
}

Here is a demo code of ESP8266 as TCP SSL client . It is based on ESP8266 SDK without OS.

It just like ESP8266 to be normal TCP client except change espconn_xxx to be espconn_secure_xxx

If your SSL packet is larger than 2048 bytes, please try to call espconn_secure_set_size to enlarge SSL buffer size (max:8192 )

#include "espconn.h"
#include "mem.h"
 
#define DNS_ENABLE
 
unsigned char *default_certificate;
unsigned int default_certificate_len = 0;
unsigned char *default_private_key;
unsigned int default_private_key_len = 0;
 
#define NET_DOMAIN "iot.espressif.cn"
 
const char* TLSHEAD = "GET / HTTP/1.1\r\nHost: %d.%d.%d.%d\r\nConnection: keep-alive\r\n\r\n";
 
#define packet_size   (2 * 1024)
 
LOCAL os_timer_t test_timer;
LOCAL struct espconn user_tcp_conn;
LOCAL struct _esp_tcp user_tcp;
ip_addr_t tcp_server_ip;
 
/******************************************************************************
 * FunctionName : user_tcp_recv_cb
 * Description  : receive callback.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_tcp_recv_cb(void *arg, char *pusrdata, unsigned short length)
{
   //received some data from tcp connection
    
    os_printf("Received data string: %s \r\n", pusrdata);
    
}
/******************************************************************************
 * FunctionName : user_tcp_sent_cb
 * Description  : data sent callback.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_tcp_sent_cb(void *arg)
{
   //data sent successfully
 
    os_printf("Sent callback: data sent successfully.\r\n");
}
/******************************************************************************
 * FunctionName : user_tcp_discon_cb
 * Description  : disconnect callback.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_tcp_discon_cb(void *arg)
{
   //tcp disconnect successfully
    
    os_printf("Disconnected from server.\r\n");
}
/******************************************************************************
 * FunctionName : user_esp_platform_sent
 * Description  : Processing the application data and sending it to the host
 * Parameters   : pespconn -- the espconn used to connetion with the host
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_send_data(struct espconn *pespconn)
{
   char *pbuf = (char *)os_zalloc(packet_size);
 
   os_sprintf(pbuf, TLSHEAD, 
    pespconn->proto.tcp->remote_ip[0], pespconn->proto.tcp->remote_ip[1], 
    pespconn->proto.tcp->remote_ip[2], pespconn->proto.tcp->remote_ip[3]);
 
   espconn_secure_send(pespconn, pbuf, os_strlen(pbuf));
    
   os_free(pbuf);
 
}
 
/******************************************************************************
 * FunctionName : user_tcp_connect_cb
 * Description  : A new incoming tcp connection has been connected.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_tcp_connect_cb(void *arg)
{
    struct espconn *pespconn = arg;
 
    os_printf("Connected to server...\r\n");
 
    espconn_regist_recvcb(pespconn, user_tcp_recv_cb);
    espconn_regist_sentcb(pespconn, user_tcp_sent_cb);
    
    user_send_data(pespconn);
}
 
/******************************************************************************
 * FunctionName : user_tcp_recon_cb
 * Description  : reconnect callback, error occured in TCP connection.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_tcp_recon_cb(void *arg, sint8 err)
{
   //error occured , tcp connection broke. user can try to reconnect here. 
    
    os_printf("Reconnect callback called, error code: %d !!! \r\n",err);
}
 
#ifdef DNS_ENABLE
/******************************************************************************
 * FunctionName : user_dns_found
 * Description  : dns found callback
 * Parameters   : name -- pointer to the name that was looked up.
 *                ipaddr -- pointer to an ip_addr_t containing the IP address of
 *                the hostname, or NULL if the name could not be found (or on any
 *                other error).
 *                callback_arg -- a user-specified callback argument passed to
 *                dns_gethostbyname
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_dns_found(const char *name, ip_addr_t *ipaddr, void *arg)
{
    struct espconn *pespconn = (struct espconn *)arg;
 
    if (ipaddr == NULL) 
   {
        os_printf("user_dns_found NULL \r\n");
        return;
    }
 
   //dns got ip
    os_printf("user_dns_found %d.%d.%d.%d \r\n",
            *((uint8 *)&ipaddr->addr), *((uint8 *)&ipaddr->addr + 1),
            *((uint8 *)&ipaddr->addr + 2), *((uint8 *)&ipaddr->addr + 3));
 
    if (tcp_server_ip.addr == 0 && ipaddr->addr != 0) 
   {
      // dns succeed, create tcp connection
        os_timer_disarm(&test_timer);
        tcp_server_ip.addr = ipaddr->addr;
        os_memcpy(pespconn->proto.tcp->remote_ip, &ipaddr->addr, 4); // remote ip of tcp server which get by dns
 
        pespconn->proto.tcp->remote_port = 8443; // remote SSL port of tcp server
       
        pespconn->proto.tcp->local_port = espconn_port(); //local port of ESP8266
 
        espconn_regist_connectcb(pespconn, user_tcp_connect_cb); // register connect callback
        espconn_regist_reconcb(pespconn, user_tcp_recon_cb); // register reconnect callback as error handler
        espconn_regist_disconcb(pespconn, user_tcp_discon_cb);  // register disconnect callback here, because that SSL handshake may fail.
         
       //espconn_secure_set_size(ESPCONN_CLIENT,5120); // set SSL buffer size, if your SSL packet larger than 2048 bytes
        espconn_secure_connect(pespconn); // tcp SSL connect
    }
}
 
/******************************************************************************
 * FunctionName : user_esp_platform_dns_check_cb
 * Description  : 1s time callback to check dns found
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
user_dns_check_cb(void *arg)
{
    struct espconn *pespconn = arg;
 
    espconn_gethostbyname(pespconn, NET_DOMAIN, &tcp_server_ip, user_dns_found); // recall DNS function
 
    os_timer_arm(&test_timer, 1000, 0);
}
#endif
 
/******************************************************************************
 * FunctionName : user_check_ip
 * Description  : check whether get ip addr or not
 * Parameters   : none
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_check_ip(void)
{
    struct ip_info ipconfig;
 
   //disarm timer first
    os_timer_disarm(&test_timer);
 
   //get ip info of ESP8266 station
    wifi_get_ip_info(STATION_IF, &ipconfig);
 
    if (wifi_station_get_connect_status() == STATION_GOT_IP && ipconfig.ip.addr != 0) 
   {
      os_printf("Connected to router and assigned IP!\r\n");
 
      // Connect to tcp server as NET_DOMAIN
      user_tcp_conn.proto.tcp = &user_tcp;
      user_tcp_conn.type = ESPCONN_TCP;
      user_tcp_conn.state = ESPCONN_NONE;
 
      #ifdef DNS_ENABLE
      tcp_server_ip.addr = 0;
       espconn_gethostbyname(&user_tcp_conn, NET_DOMAIN, &tcp_server_ip, user_dns_found); // DNS function
 
       os_timer_setfn(&test_timer, (os_timer_func_t *)user_dns_check_cb, &user_tcp_conn);
       os_timer_arm(&test_timer, 1000, 0);
      #else
       const char esp_server_ip[4] = {192, 185, 229, 242};
 
       os_memcpy(user_tcp_conn.proto.tcp->remote_ip, esp_server_ip, 4);
 
       user_tcp_conn.proto.tcp->remote_port = 443; // remote SSL port of tcp server
       
       user_tcp_conn.proto.tcp->local_port = espconn_port(); //local port of ESP8266
 
       espconn_regist_connectcb(&user_tcp_conn, user_tcp_connect_cb); // register connect callback
       espconn_regist_reconcb(&user_tcp_conn, user_tcp_recon_cb); // register reconnect callback as error handler
 
       espconn_secure_set_size(ESPCONN_CLIENT,5120); // set SSL buffer size, if your SSL packet larger than 2048 bytes
       espconn_secure_connect(&user_tcp_conn); // tcp SSL connect
      #endif
 
    } 
   else
   {
        
        if ((wifi_station_get_connect_status() == STATION_WRONG_PASSWORD ||
                wifi_station_get_connect_status() == STATION_NO_AP_FOUND ||
                wifi_station_get_connect_status() == STATION_CONNECT_FAIL)) 
        {
         os_printf("Connection to router failed.\r\n");
        } 
      else
      {
           //re-arm timer to check ip
            os_timer_setfn(&test_timer, (os_timer_func_t *)user_check_ip, NULL);
            os_timer_arm(&test_timer, 100, 0);
        }
    }
}
 
 
/******************************************************************************
 * FunctionName : user_set_station_config
 * Description  : set the router info which ESP8266 station will connect to 
 * Parameters   : none
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_set_station_config(void)
{
   // Wifi configuration 
   char ssid[32] = SSID; 
   char password[64] = PASSWORD; 
   struct station_config stationConf; 
 
   //need not mac address
   stationConf.bssid_set = 0; 
    
   //Set ap settings 
   os_memcpy(&stationConf.ssid, ssid, 32); 
   os_memcpy(&stationConf.password, password, 64); 
   wifi_station_set_config(&stationConf); 
 
   //set a timer to check whether got ip from router succeed or not.
   os_timer_disarm(&test_timer);
    os_timer_setfn(&test_timer, (os_timer_func_t *)user_check_ip, NULL);
    os_timer_arm(&test_timer, 100, 0);
 
}
 
 
/******************************************************************************
 * FunctionName : user_init
 * Description  : entry of user application, init user function here
 * Parameters   : none
 * Returns      : none
*******************************************************************************/
void user_init(void)
{
    os_printf("SDK version:%s\n", system_get_sdk_version());
    
   //Set station mode 
   wifi_set_opmode(STATION_MODE); 
 
   //ESP8266 connect to router
   user_set_station_config();
 
}

Sample code below is based on ESP8266 SDK without OS.

1. Start from user_init

2. ESP8266 is in station mode and connect to a router

3. Set up a TCP server listening to TCP client

4. If TCP server received data from TCP client, it will reply the same data back to TCP client.

Note: for ESP8266_RTOS_SDK, please call espconn_init() in the user_init to initialize espconn first.

#include "ets_sys.h"
#include "osapi.h"
#include "user_interface.h"
#include "espconn.h"

LOCAL struct espconn esp_conn;
LOCAL esp_tcp esptcp;

#define SERVER_LOCAL_PORT   1112

/******************************************************************************
 * FunctionName : tcp_server_sent_cb
 * Description  : data sent callback.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
tcp_server_sent_cb(void *arg)
{
   //data sent successfully

    os_printf("tcp sent cb \r\n");
}


/******************************************************************************
 * FunctionName : tcp_server_recv_cb
 * Description  : receive callback.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
tcp_server_recv_cb(void *arg, char *pusrdata, unsigned short length)
{
   //received some data from tcp connection
   
   struct espconn *pespconn = arg;
   os_printf("tcp recv : %s \r\n", pusrdata);
   
   espconn_sent(pespconn, pusrdata, length);
   
}

/******************************************************************************
 * FunctionName : tcp_server_discon_cb
 * Description  : disconnect callback.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
tcp_server_discon_cb(void *arg)
{
   //tcp disconnect successfully
   
    os_printf("tcp disconnect succeed !!! \r\n");
}

/******************************************************************************
 * FunctionName : tcp_server_recon_cb
 * Description  : reconnect callback, error occured in TCP connection.
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
tcp_server_recon_cb(void *arg, sint8 err)
{
   //error occured , tcp connection broke. 
   
    os_printf("reconnect callback, error code %d !!! \r\n",err);
}

LOCAL void tcp_server_multi_send(void)
{
   struct espconn *pesp_conn = &esp_conn;

   remot_info *premot = NULL;
   uint8 count = 0;
   sint8 value = ESPCONN_OK;
   if (espconn_get_connection_info(pesp_conn,&premot,0) == ESPCONN_OK){
      char *pbuf = "tcp_server_multi_send\n";
      for (count = 0; count < pesp_conn->link_cnt; count ++){
         pesp_conn->proto.tcp->remote_port = premot[count].remote_port;
         
         pesp_conn->proto.tcp->remote_ip[0] = premot[count].remote_ip[0];
         pesp_conn->proto.tcp->remote_ip[1] = premot[count].remote_ip[1];
         pesp_conn->proto.tcp->remote_ip[2] = premot[count].remote_ip[2];
         pesp_conn->proto.tcp->remote_ip[3] = premot[count].remote_ip[3];

         espconn_sent(pesp_conn, pbuf, os_strlen(pbuf));
      }
   }
}


/******************************************************************************
 * FunctionName : tcp_server_listen
 * Description  : TCP server listened a connection successfully
 * Parameters   : arg -- Additional argument to pass to the callback function
 * Returns      : none
*******************************************************************************/
LOCAL void ICACHE_FLASH_ATTR
tcp_server_listen(void *arg)
{
    struct espconn *pesp_conn = arg;
    os_printf("tcp_server_listen !!! \r\n");

    espconn_regist_recvcb(pesp_conn, tcp_server_recv_cb);
    espconn_regist_reconcb(pesp_conn, tcp_server_recon_cb);
    espconn_regist_disconcb(pesp_conn, tcp_server_discon_cb);
    
    espconn_regist_sentcb(pesp_conn, tcp_server_sent_cb);
   tcp_server_multi_send();
}

/******************************************************************************
 * FunctionName : user_tcpserver_init
 * Description  : parameter initialize as a TCP server
 * Parameters   : port -- server port
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_tcpserver_init(uint32 port)
{
    esp_conn.type = ESPCONN_TCP;
    esp_conn.state = ESPCONN_NONE;
    esp_conn.proto.tcp = &esptcp;
    esp_conn.proto.tcp->local_port = port;
    espconn_regist_connectcb(&esp_conn, tcp_server_listen);

    sint8 ret = espconn_accept(&esp_conn);
    
    os_printf("espconn_accept [%d] !!! \r\n", ret);

}
LOCAL os_timer_t test_timer;

/******************************************************************************
 * FunctionName : user_esp_platform_check_ip
 * Description  : check whether get ip addr or not
 * Parameters   : none
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_esp_platform_check_ip(void)
{
    struct ip_info ipconfig;

   //disarm timer first
    os_timer_disarm(&test_timer);

   //get ip info of ESP8266 station
    wifi_get_ip_info(STATION_IF, &ipconfig);

    if (wifi_station_get_connect_status() == STATION_GOT_IP && ipconfig.ip.addr != 0) {

      os_printf("got ip !!! \r\n");
      user_tcpserver_init(SERVER_LOCAL_PORT);

    } else {
       
        if ((wifi_station_get_connect_status() == STATION_WRONG_PASSWORD ||
                wifi_station_get_connect_status() == STATION_NO_AP_FOUND ||
                wifi_station_get_connect_status() == STATION_CONNECT_FAIL)) {
                
         os_printf("connect fail !!! \r\n");
         
        } else {
        
           //re-arm timer to check ip
            os_timer_setfn(&test_timer, (os_timer_func_t *)user_esp_platform_check_ip, NULL);
            os_timer_arm(&test_timer, 100, 0);
        }
    }
}

/******************************************************************************
 * FunctionName : user_set_station_config
 * Description  : set the router info which ESP8266 station will connect to 
 * Parameters   : none
 * Returns      : none
*******************************************************************************/
void ICACHE_FLASH_ATTR
user_set_station_config(void)
{
   // Wifi configuration 
   char ssid[32] = SSID; 
   char password[64] = PASSWORD; 
   struct station_config stationConf; 

   //need not mac address
   stationConf.bssid_set = 0; 
   
   //Set ap settings 
   os_memcpy(&stationConf.ssid, ssid, 32); 
   os_memcpy(&stationConf.password, password, 64); 
   wifi_station_set_config(&stationConf); 

   //set a timer to check whether got ip from router succeed or not.
   os_timer_disarm(&test_timer);
   os_timer_setfn(&test_timer, (os_timer_func_t *)user_esp_platform_check_ip, NULL);
   os_timer_arm(&test_timer, 100, 0);

}

/******************************************************************************
 * FunctionName : user_init
 * Description  : entry of user application, init user function here
 * Parameters   : none
 * Returns      : none
*******************************************************************************/
void user_init(void)
{
    os_printf("SDK version:%s\n", system_get_sdk_version());
   
   //Set  station mode 
   wifi_set_opmode(STATIONAP_MODE); 

   // ESP8266 connect to router.
   user_set_station_config();
   
}