UDP server and UDP client

UDP socket server uses 1500 as port in local machine.

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <unistd.h> /* close() */
#include <string.h> /* memset() */

#define LOCAL_SERVER_PORT 1500
#define MAX_MSG 100

int main(int argc, char *argv[])
{
 int sd, rc, n, cliLen;
 struct sockaddr_in cliAddr, servAddr;
 char msg[MAX_MSG];

 /* socket creation */
 sd=socket(AF_INET, SOCK_DGRAM, 0);
 if(sd<0) {
   printf("%s: cannot open socket \n",argv[0]);
   exit(1);
 }

 /* bind local server port */
 servAddr.sin_family = AF_INET;
 servAddr.sin_addr.s_addr = htonl(INADDR_ANY);
 servAddr.sin_port = htons(LOCAL_SERVER_PORT);
 rc = bind (sd, (struct sockaddr *) &servAddr,sizeof(servAddr));
 if(rc<0) {
   printf("%s: cannot bind port number %d \n",
      argv[0], LOCAL_SERVER_PORT);
   exit(1);
 }

 printf("%s: waiting for data on port UDP %u\n",
      argv[0],LOCAL_SERVER_PORT);

 /* server infinite loop */
 while(1) {
      /* init buffer */
   memset(msg,0x0,MAX_MSG);

   /* receive message */
   cliLen = sizeof(cliAddr);
   n = recvfrom(sd, msg, MAX_MSG, 0,
        (struct sockaddr *) &cliAddr, &cliLen);

   if(n<0) {
     printf("%s: cannot receive data \n",argv[0]);
     continue;
   }
    
   /* print received message */
   printf("%s: from %s:UDP%u : %s \n",
      argv[0],inet_ntoa(cliAddr.sin_addr),
      ntohs(cliAddr.sin_port),msg);
  
 }/* end of server infinite loop */
}

gcc -g -o udpserver udpserver.c
./udpserver

Start the server first and then start the UDP client to send packages to it.
./udpclient 10.50.58.132 111 222 333

#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <unistd.h>
#include <string.h> /* memset() */
#include <sys/time.h> /* select() */

#define REMOTE_SERVER_PORT 1500
#define MAX_MSG 100

int main(int argc, char *argv[]) {

 int sd, rc, i;
 struct sockaddr_in cliAddr, remoteServAddr;
 struct hostent *h;

 /* check command line args */
 if(argc<3) {
   printf("usage : %s <server> <data1> ... <dataN> \n", argv[0]);
   exit(1);
 }

 /* get server IP address (no check if input is IP address or DNS name */
 h = gethostbyname(argv[1]);
 if(h==NULL) {
   printf("%s: unknown host '%s' \n", argv[0], argv[1]);
   exit(1);
 }

 printf("%s: sending data to '%s' (IP : %s) \n", argv[0], h->h_name,
    inet_ntoa(*(struct in_addr *)h->h_addr_list[0]));

 remoteServAddr.sin_family = h->h_addrtype;
 memcpy((char *) &remoteServAddr.sin_addr.s_addr,
    h->h_addr_list[0], h->h_length);
 remoteServAddr.sin_port = htons(REMOTE_SERVER_PORT);

 /* socket creation */
 sd = socket(AF_INET,SOCK_DGRAM,0);
 if(sd<0) {
   printf("%s: cannot open socket \n",argv[0]);
   exit(1);
 }

 /* bind any port */
 cliAddr.sin_family = AF_INET;
 cliAddr.sin_addr.s_addr = htonl(INADDR_ANY);
 cliAddr.sin_port = htons(0);

 rc = bind(sd, (struct sockaddr *) &cliAddr, sizeof(cliAddr));
 if(rc<0) {
   printf("%s: cannot bind port\n", argv[0]);
   exit(1);
 }

 /* send data */
 for(i=2;i<argc;i++) {
   rc = sendto(sd, argv[i], strlen(argv[i])+1, 0,
       (struct sockaddr *) &remoteServAddr,
       sizeof(remoteServAddr));

   if(rc<0) {
     printf("%s: cannot send data %d \n",argv[0],i-1);
     close(sd);
     exit(1);
   }

 }
}