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picohttps.c
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picohttps.c
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/* Pico HTTPS request example *************************************************
* *
* An HTTPS client example for the Raspberry Pi Pico W *
* *
* A simple yet complete example C application which sends a single request *
* to a web server over HTTPS and reads the resulting response. *
* *
******************************************************************************/
/* Includes *******************************************************************/
// Pico SDK
#include "pico/stdlib.h" // Standard library
#include "pico/cyw43_arch.h" // Pico W wireless
// lwIP
#include "lwip/dns.h" // Hostname resolution
#include "lwip/altcp_tls.h" // TCP + TLS (+ HTTP == HTTPS)
#include "lwip/prot/iana.h" // HTTPS port number
// Pico HTTPS request example
#include "picohttps.h" // Options, macros, forward declarations
/* Main ***********************************************************************/
void main(void){
// Initialise standard I/O over USB
if(!init_stdio()) return;
// Initialise Pico W wireless hardware
printf("Initializing CYW43\n");
if(!init_cyw43()){
printf("Failed to initialize CYW43\n");
return;
}
printf("Initialized CYW43\n");
// Connect to wireless network
printf("Connecting to %s\n", PICOHTTPS_WIFI_SSID);
if(!connect_to_network()){
printf("Failed to connect to %s\n", PICOHTTPS_WIFI_SSID);
cyw43_arch_deinit(); // Deinit Pico W wireless hardware
return;
}
printf("Connected to %s\n", PICOHTTPS_WIFI_SSID);
// Resolve server hostname
ip_addr_t ipaddr;
char* char_ipaddr;
printf("Resolving %s\n", PICOHTTPS_HOSTNAME);
if(!resolve_hostname(&ipaddr)){
printf("Failed to resolve %s\n", PICOHTTPS_HOSTNAME);
// TODO: Disconnect from network
cyw43_arch_deinit(); // Deinit Pico W wireless hardware
return;
}
cyw43_arch_lwip_begin();
char_ipaddr = ipaddr_ntoa(&ipaddr);
cyw43_arch_lwip_end();
printf("Resolved %s (%s)\n", PICOHTTPS_HOSTNAME, char_ipaddr);
// Establish TCP + TLS connection with server
struct altcp_pcb* pcb = NULL;
printf("Connecting to https://%s:%d\n", char_ipaddr, LWIP_IANA_PORT_HTTPS);
if(!connect_to_host(&ipaddr, &pcb)){
printf("Failed to connect to https://%s:%d\n", char_ipaddr, LWIP_IANA_PORT_HTTPS);
// TODO: Disconnect from network
cyw43_arch_deinit(); // Deinit Pico W wireless hardware
return;
}
printf("Connected to https://%s:%d\n", char_ipaddr, LWIP_IANA_PORT_HTTPS);
// Send HTTP request to server
printf("Sending request\n");
if(!send_request(pcb)){
printf("Failed to send request\n");
altcp_free_config( // Free connection configuration
((struct altcp_callback_arg*)(pcb->arg))->config
);
altcp_free_arg( // Free connection callback argument
(struct altcp_callback_arg*)(pcb->arg)
);
altcp_free_pcb(pcb); // Free connection PCB
// TODO: Disconnect from network
cyw43_arch_deinit(); // Deinit Pico W wireless hardware
return;
}
printf("Request sent\n");
// Await HTTP response
printf("Awaiting response\n");
sleep_ms(5000);
printf("Awaited response\n");
// Return
printf("Exiting\n");
return;
//printf("Exited 😉 \n");
}
/* Functions ******************************************************************/
// Initialise standard I/O over USB
bool init_stdio(void){
if(!stdio_usb_init()) return false;
stdio_set_translate_crlf(&stdio_usb, false);
return true;
}
// Initialise Pico W wireless hardware
bool init_cyw43(void){
return !((bool)cyw43_arch_init_with_country(PICOHTTPS_INIT_CYW43_COUNTRY));
}
// Connect to wireless network
bool connect_to_network(void){
cyw43_arch_enable_sta_mode();
return !(
(bool)cyw43_arch_wifi_connect_timeout_ms(
PICOHTTPS_WIFI_SSID,
PICOHTTPS_WIFI_PASSWORD,
CYW43_AUTH_WPA2_AES_PSK,
PICOHTTPS_WIFI_TIMEOUT
)
);
}
// Resolve hostname
bool resolve_hostname(ip_addr_t* ipaddr){
// Zero address
ipaddr->addr = IPADDR_ANY;
// Attempt resolution
cyw43_arch_lwip_begin();
lwip_err_t lwip_err = dns_gethostbyname(
PICOHTTPS_HOSTNAME,
ipaddr,
callback_gethostbyname,
ipaddr
);
cyw43_arch_lwip_end();
if(lwip_err == ERR_INPROGRESS){
// Await resolution
//
// IP address will be made available shortly (by callback) upon DNS
// query response.
//
while(ipaddr->addr == IPADDR_ANY)
sleep_ms(PICOHTTPS_RESOLVE_POLL_INTERVAL);
if(ipaddr->addr != IPADDR_NONE)
lwip_err = ERR_OK;
}
// Return
return !((bool)lwip_err);
}
// Free TCP + TLS protocol control block
void altcp_free_pcb(struct altcp_pcb* pcb){
cyw43_arch_lwip_begin();
lwip_err_t lwip_err = altcp_close(pcb); // Frees PCB
cyw43_arch_lwip_end();
while(lwip_err != ERR_OK)
sleep_ms(PICOHTTPS_ALTCP_CONNECT_POLL_INTERVAL);
cyw43_arch_lwip_begin();
lwip_err = altcp_close(pcb); // Frees PCB
cyw43_arch_lwip_end();
}
// Free TCP + TLS connection configuration
void altcp_free_config(struct altcp_tls_config* config){
cyw43_arch_lwip_begin();
altcp_tls_free_config(config);
cyw43_arch_lwip_end();
}
// Free TCP + TLS connection callback argument
void altcp_free_arg(struct altcp_callback_arg* arg){
if(arg){
free(arg);
}
}
// Establish TCP + TLS connection with server
bool connect_to_host(ip_addr_t* ipaddr, struct altcp_pcb** pcb){
// Instantiate connection configuration
u8_t ca_cert[] = PICOHTTPS_CA_ROOT_CERT;
cyw43_arch_lwip_begin();
struct altcp_tls_config* config = altcp_tls_create_config_client(
ca_cert,
LEN(ca_cert)
);
cyw43_arch_lwip_end();
if(!config) return false;
// Instantiate connection PCB
//
// Can also do this more generically using;
//
// altcp_allocator_t allocator = {
// altcp_tls_alloc, // Allocator function
// config // Allocator function argument (state)
// };
// altcp_new(&allocator);
//
// No benefit in doing this though; altcp_tls_alloc calls altcp_tls_new
// under the hood anyway.
//
cyw43_arch_lwip_begin();
*pcb = altcp_tls_new(config, IPADDR_TYPE_V4);
cyw43_arch_lwip_end();
if(!(*pcb)){
altcp_free_config(config);
return false;
}
// Configure common argument for connection callbacks
//
// N.b. callback argument must be in scope in callbacks. As callbacks may
// fire after current function returns, cannot declare argument locally,
// but rather should allocate on the heap. Must then ensure allocated
// memory is subsequently freed.
//
struct altcp_callback_arg* arg = malloc(sizeof(*arg));
if(!arg){
altcp_free_pcb(*pcb);
altcp_free_config(config);
return false;
}
arg->config = config;
arg->connected = false;
cyw43_arch_lwip_begin();
altcp_arg(*pcb, (void*)arg);
cyw43_arch_lwip_end();
// Configure connection fatal error callback
cyw43_arch_lwip_begin();
altcp_err(*pcb, callback_altcp_err);
cyw43_arch_lwip_end();
// Configure idle connection callback (and interval)
cyw43_arch_lwip_begin();
altcp_poll(
*pcb,
callback_altcp_poll,
PICOHTTPS_ALTCP_IDLE_POLL_INTERVAL
);
cyw43_arch_lwip_end();
// Configure data acknowledge callback
cyw43_arch_lwip_begin();
altcp_sent(*pcb, callback_altcp_sent);
cyw43_arch_lwip_end();
// Configure data reception callback
cyw43_arch_lwip_begin();
altcp_recv(*pcb, callback_altcp_recv);
cyw43_arch_lwip_end();
// Send connection request (SYN)
cyw43_arch_lwip_begin();
lwip_err_t lwip_err = altcp_connect(
*pcb,
ipaddr,
LWIP_IANA_PORT_HTTPS,
callback_altcp_connect
);
cyw43_arch_lwip_end();
// Connection request sent
if(lwip_err == ERR_OK){
// Await connection
//
// Sucessful connection will be confirmed shortly in
// callback_altcp_connect.
//
while(!(arg->connected))
sleep_ms(PICOHTTPS_ALTCP_CONNECT_POLL_INTERVAL);
} else {
// Free allocated resources
altcp_free_pcb(*pcb);
altcp_free_config(config);
altcp_free_arg(arg);
}
// Return
return !((bool)lwip_err);
}
// Send HTTP request
bool send_request(struct altcp_pcb* pcb){
const char request[] = PICOHTTPS_REQUEST;
// Check send buffer and queue length
//
// Docs state that altcp_write() returns ERR_MEM on send buffer too small
// _or_ send queue too long. Could either check both before calling
// altcp_write, or just handle returned ERR_MEM — which is preferable?
//
//if(
// altcp_sndbuf(pcb) < (LEN(request) - 1)
// || altcp_sndqueuelen(pcb) > TCP_SND_QUEUELEN
//) return -1;
// Write to send buffer
cyw43_arch_lwip_begin();
lwip_err_t lwip_err = altcp_write(pcb, request, LEN(request) -1, 0);
cyw43_arch_lwip_end();
// Written to send buffer
if(lwip_err == ERR_OK){
// Output send buffer
((struct altcp_callback_arg*)(pcb->arg))->acknowledged = 0;
cyw43_arch_lwip_begin();
lwip_err = altcp_output(pcb);
cyw43_arch_lwip_end();
// Send buffer output
if(lwip_err == ERR_OK){
// Await acknowledgement
while(
!((struct altcp_callback_arg*)(pcb->arg))->acknowledged
) sleep_ms(PICOHTTPS_HTTP_RESPONSE_POLL_INTERVAL);
if(
((struct altcp_callback_arg*)(pcb->arg))->acknowledged
!= (LEN(request) - 1)
) lwip_err = -1;
}
}
// Return
return !((bool)lwip_err);
}
// DNS response callback
void callback_gethostbyname(
const char* name,
const ip_addr_t* resolved,
void* ipaddr
){
if(resolved) *((ip_addr_t*)ipaddr) = *resolved; // Successful resolution
else ((ip_addr_t*)ipaddr)->addr = IPADDR_NONE; // Failed resolution
}
// TCP + TLS connection error callback
void callback_altcp_err(void* arg, lwip_err_t err){
// Print error code
printf("Connection error [lwip_err_t err == %d]\n", err);
// Free ALTCP TLS config
if( ((struct altcp_callback_arg*)arg)->config )
altcp_free_config( ((struct altcp_callback_arg*)arg)->config );
// Free ALTCP callback argument
altcp_free_arg((struct altcp_callback_arg*)arg);
}
// TCP + TLS connection idle callback
lwip_err_t callback_altcp_poll(void* arg, struct altcp_pcb* pcb){
// Callback not currently used
return ERR_OK;
}
// TCP + TLS data acknowledgement callback
lwip_err_t callback_altcp_sent(void* arg, struct altcp_pcb* pcb, u16_t len){
((struct altcp_callback_arg*)arg)->acknowledged = len;
return ERR_OK;
}
// TCP + TLS data reception callback
lwip_err_t callback_altcp_recv(
void* arg,
struct altcp_pcb* pcb,
struct pbuf* buf,
lwip_err_t err
){
// Store packet buffer at head of chain
//
// Required to free entire packet buffer chain after processing.
//
struct pbuf* head = buf;
switch(err){
// No error receiving
case ERR_OK:
// Handle packet buffer chain
//
// * buf->tot_len == buf->len — Last buf in chain
// * && buf->next == NULL — last buf in chain, no packets in queue
// * && buf->next != NULL — last buf in chain, more packets in queue
//
if(buf){
// Print packet buffer
u16_t i;
while(buf->len != buf->tot_len){
for(i = 0; i < buf->len; i++) putchar(((char*)buf->payload)[i]);
buf = buf->next;
}
for(i = 0; i < buf->len; i++) putchar(((char*)buf->payload)[i]);
assert(buf->next == NULL);
// Advertise data reception
altcp_recved(pcb, head->tot_len);
}
// …fall-through…
case ERR_ABRT:
// Free buf
pbuf_free(head); // Free entire pbuf chain
// Reset error
err = ERR_OK; // Only return ERR_ABRT when calling tcp_abort()
}
// Return error
return err;
}
// TCP + TLS connection establishment callback
lwip_err_t callback_altcp_connect(
void* arg,
struct altcp_pcb* pcb,
lwip_err_t err
){
((struct altcp_callback_arg*)arg)->connected = true;
return ERR_OK;
}