multithreading - Concurrent TCP server in C that adjust its size. -

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my aim create server connected many clients (but rather limited number). clients running on mobile phones in lan. there can 2 mobile phones, can 10 mobile phones. wouldn't limit max number of phones ahead.

i think tcp communication phone rather longer (not simple request/response rather longer dialog between both). thread pool seems better suited many connection, rather short request/response.

i think best using simple pthreads. possibly create 1 pthread per 1 connection mobile phone.

but here may doubts there can appear many such connections , number of pthreads large. think limiting number of connections example 10 @ same time , in order next mobile phone able connect such server there connected phone must disconnect.

i have done this: 

    int cs_fd;      printf("waiting new connections on main thread...\n");      while(1) {         cs_fd = accept_new_connection(ps_fd);          if(cs_fd == failure) {             fprintf(stderr, "accept_new_connection: failed!\n");             return failure;         } else if(cs_fd == continue) {             continue;         }          // handle new connection on concurrent thread         connection_thread(cs_fd, conn_handler);     }

but doesn't limit number of threads , connection. how can such thing?

  1. limit number of child threads max_num_of_threads.
  2. accept() new connection if limit not exceeded.
  3. if num of child thread equal max_num_of_threads wait accepting new connection until else disconnects.
  4. if disconnects can accept new connection.
  5. client should info cannot connect because there many connections (connected devices) , must wait.

i think this: 

int cs_fd;  pthread_t conn_threads[max_num_of_threads];   printf("waiting new connections on main thread...\n");   while(1) {   for(int i=0; i<max_num_of_threads; i++) {       cs_fd = accept_new_connection(ps_fd);        // check cs_fd correct       conn_threads[i] = connection_thread(cs_fd, conn_handler);  }   // here problem waits until child threads finish // not 1 resume accepting new connections  for(int i=0; i<max_num_of_threads; i++) {      pthread_join(&conn_threads[i], null);  }  }

now think whether usage of waiting/signaling couldn't help. maybe usage of pthread_cond_wait() when there max limit reached , pthread_cond_signal() when child thread exiting.

in case of client know why cannot connect maybe should make separate thread separate udp server request/response exchange of server status codes.

is there reason want spawn threads each connection? why not have list of connections, use 'select()' see who's sending info, , deal info. if dealing info takes while, can hand off threads (if free).

that's kind of pushing problem further processing, possible if keep pushing , pushing down need it, may not need threads @ all.


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