Reza - good advice. To check connection status, I try to write to the socket
and then check if the return code (# bytes written) is < 0 - correct? Or is
there another status check that you are referring to?
On Wednesday, July 22, 2020, 10:44:13 AM CDT, Reza Mahdi
<[email protected]> wrote:
In fact, you may not relay on other program's behavior. Your app must be
failed tolerant. So, after any event that may occur, check the status.
Suppose the connection get dropped by a wire disconnect....
Get ready for anything
On Wed, Jul 22, 2020, 20:09 Bill Engelke <[email protected]> wrote:
Thanks for the feedback. A follow-up question: My heartbeat runs only once a
minute (or even less); if I would like to let the server close the connection
each time (and re-establish it the next time), could I just let it close the
connection, and not change that?
On Tuesday, July 21, 2020 at 10:01:57 AM UTC-5, Reza Mahdi wrote:
Well, you are using HTTP 1.0In this version, after the server sends the
response, it will close the connection.You may use HTTP 1.1 with "Connection:
keep-alive" header, to signal the server not to close the connection.
On Tue, Jul 21, 2020, 19:24 Bill Engelke <[email protected]> wrote:
I need code that will send a "heartbeat" to a web service (say, once per
minute), and receive a response. This works fine with a browser, so I know the
server is reachable and responding correctly. I have tried a vast number of
different ways of doing this using libuv and c code, and so far, partial
success at best. I have been able to connect to the server and send a request;
but only the first request would work, and further sends would not make it to
the server. In my most recent attempts, even the connection request stopped
working. I don't know if the problem is my incorrect use of libuv, or something
in the networking part that I don't understand. I have put the code into a
single app for testing below; can anyone offer any suggestions??
```
#include <stdio.h>
#include <stdlib.h>
#include <uv.h>
#include <string.h>
#include <unistd.h>
typedef struct {
uv_write_t req;
uv_buf_t buf;
} write_req_t;
static uv_tcp_t* socket_central;
static struct sockaddr_in central_dest;
static void alloc_buffer(uv_handle_t* handle, size_t suggested_size, uv_buf_t*
buf) {
buf->base = malloc(suggested_size);
buf->len = suggested_size;
}
uv_loop_t *loop;
///// Callback for after TCP stream is closed //////////////////
void on_close(uv_handle_t * handle)
{
printf("uv close triggered\n");
}
// process response from central server
void proc_central_response(uv_stream_t *central, ssize_t nread, const uv_buf_t
*buf)
{
printf("RESPONSE from Central Control; nread=%li\n",nread);
printf("---------------------------------------------------------------\n");
if (nread > 0) {
printf("buf='%s'\n",buf->base);
printf("---------------------------------------------------------------\n");
}
if (nread < 0) {
if (nread != UV_EOF)
fprintf(stderr, "Read error %s\n", uv_err_name(nread));
free(buf->base);
uv_close((uv_handle_t*) central, on_close);
return;
}
//uv_close((uv_handle_t*) central, on_close);
free(buf->base);
return;
}
// now connected; send http POST
void on_central_connect(uv_connect_t* connection, int status)
{
uv_stream_t* stream;
uv_write_t write_req;
printf("Connected to Central Contro, status = %il\n",status);
if (status < 0) {
fprintf(stderr, "Error in in connecting to Central Control %s\n",
uv_strerror(status));
// error!
return;
}
printf(" - - - - Connect to Central Control - - - ;\n");
// get the handle to the stream passed in connection
stream = connection->handle;
// make ready to receive response from Central
uv_read_start((uv_stream_t*) stream, alloc_buffer, proc_central_response);
// Now, prepare a heartbeat message to send to Central Control
struct timeval timeout;
char message[1024];
timeout.tv_sec = 10; // if Central Host doesn't respond, we ignore
timeout.tv_usec = 0; // and will try again after the pause time
char tbuf[30];
struct timeval tv;
time_t curtime;
char mytoken[75];
strcpy(mytoken,"T12345XYZ"); // hard code this for now
gettimeofday(&tv, NULL);
curtime = tv.tv_sec;
strftime(tbuf, 30, "%m-%d-%Y-%T.",localtime(&curtime));
printf("Heartbeat TOD: '%s' %ld\n",tbuf,tv.tv_usec);
// write message to go to host
// message contains identity token and time stamp
sprintf(message,"POST /apikey/%s-%s HTTP/1.0\r\n\r\n",mytoken,tbuf);
uv_buf_t buf = uv_buf_init(message,strlen(message));
int r1 = uv_write(&write_req, stream, &buf, 1, NULL);
}
void heartbeat(void *arg) {
while(1==1)
{
printf("alloc socket\n");
socket_central = (uv_tcp_t*)malloc(sizeof(uv_tcp_t));\
printf("tcp init\n");
uv_tcp_init(loop, socket_central);
printf("alloc connection\n");
uv_connect_t* connect = (uv_connect_t*)malloc(sizeof(uv_connect_t));
uv_ip4_addr("192.168.1.67", 4000, ¢ral_dest);
printf("CONNECT TO CENTRAL\n");
uv_tcp_connect(connect, socket_central, (const struct
sockaddr*)¢ral_dest, on_central_connect);
printf("CONNECTION REQUEST DONE\n");
printf("sleep start\n");
sleep(5);
printf("sleep done\n");
}
}
int main() {
printf("start\n");
loop = uv_default_loop();
printf("alloc socket\n");
socket_central = (uv_tcp_t*)malloc(sizeof(uv_tcp_t));\
printf("tcp init\n");
uv_tcp_init(loop, socket_central);
uv_thread_t hb_id;
printf("start thread\n");
uv_thread_create(&hb_id, heartbeat, NULL);
printf("past thread start\n");
uv_run(loop, UV_RUN_DEFAULT);
sleep(10);
printf("Now quitting.\n");
uv_loop_close(loop);
//free(loop);
return 0;
}```
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