sockets - C - SIGALRM not received -

i'm new signals, i'm trying set sigalrm on udp echo service, socket programming practice.
here have udp socket, client sends string server , waits response (any response, here string echoed server).
goals set sigalrm , let client resend string few times if no responses made server or udp packets lost.

here, used small sample , simplified long lines ..., can more details on github repo (line 51)

sigalrm-client.c

unsigned int tries = 0;  void catchalarm() {     tries += 1; }  int main(int argc, char **argv) {     // skipped     // ...     struct sigaction handler;     handler.sa_handler = catchalarm;     handler.sa_flags = 0;     if(sigfillset(&handler.sa_mask) < 0)         return 1;      if(sigaction(sigalrm, &handler, 0) < 0)         return 2;      ssize_t bytes;      bytes = sendto(servsock,...);      while((bytes = recvfrom(servsock,...)) < 0) {         // alarm went off         if(errno == eintr) {             // try 5 times             if(tries < 5) {                 bytes = sendto(servsock,...);             } else {                 fprintf(stdout, "no response, waiting...\n");             }         } else {             fprintf(stdout, "failed data\n");             return 3;         }     }     // recvfrom() got something, cancel timeout     alarm(0);     fprintf(stdout, "received %d bytes of data\n", bytes);     close(servsock); } 

when run client, won't receive sigalrm signal , udp packets lost in first attempt?!
client won't retry sending string exit after 5 attempts, instead, waits server response forever!
prevents client sigalrm?
did miss here?

your code in github repo never calls alarm() non-zero number. you'll never alarm signal delivered automatically unless request one. relying on other process send process alarm signal isn't resilient.