linux - c server handle multiple connections, error on port no -

i've been experimenting server code http://www.linuxhowtos.org/c_c++/socket.htm.

the regular server code worked fine, i've changed hardcode in port number rather read command line, wanted server capable of holding multiple connections. waiting short strings come in 3 different client programs @ regular intervals.

i've compiled below i'm getting error "error, no port provided", makes no sense i've included port number.

some initial questions

• does have idea wrong?
• also, hope no 1 minds me asking question, adapted use multi-threading?

i'm using dual core mini-processor centos. needs read short amounts of data socket, passed @ regular intervals. i'm aware forking overload cpu , multi-threading may memory intensive type of machine.

are there other alternatives handling multiple socket connections worth me researching? data come in every 5 seconds, every few hours, twice day respectively.

#include <stdio.h> #include <unistd.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h>  void read_socket(int); /* function prototype */ void error(const char *msg)  {     perror(msg);     exit(1); }  int main(int argc, char *argv[]){      int store_limit=10; //user input     int store_limit_secs=store_limit * 24 * 60 * 60; //user input     int sockfd, newsockfd, portno, pid;     socklen_t clilen;     struct sockaddr_in serv_addr, cli_addr;       if (argc < 2) {          fprintf(stderr,"error, no port provided\n");          exit(1);      }      sockfd = socket(af_inet, sock_stream, 0);      if (sockfd < 0)         error("error opening socket");      bzero((char *) &serv_addr, sizeof(serv_addr));       portno = 15000;      serv_addr.sin_family = af_inet;      serv_addr.sin_addr.s_addr = inaddr_any;      serv_addr.sin_port = htons(portno);      if (bind(sockfd, (struct sockaddr *) &serv_addr,          sizeof(serv_addr)) < 0)           error("error on binding");      listen(sockfd,5);      clilen = sizeof(cli_addr);      while (1) {      newsockfd = accept(sockfd,          (struct sockaddr *) &cli_addr, &clilen);      if (newsockfd < 0)          error("error on accept");      pid = fork();      if (pid < 0)          error("error on fork");      if (pid == 0)  {          close(sockfd);          read_socket(newsockfd);          exit(0);      }      else close(newsockfd);  } /* end of while */  close(sockfd);  return 0; /* never here */ }   void read_socket (int sock) {         int n;        char buffer[256];        bzero(buffer,256);        n = read(sock,buffer,255);        if (n < 0) error("error reading socket");        printf("here message: %s\n",buffer);        n = write(sock,"i got message",18);        if (n < 0) error("error writing socket"); } 

in absence of command-line argument, argc 1, block execute, resulting program exiting:

 if (argc < 2) {      fprintf(stderr,"error, no port provided\n");      exit(1);  } 

since hardcoded value portno, can remove block.