gethostbyname on remote client but getting sometimes 'Resource temporarily unavailable' - c

Question

sometimes, expecially when client and server are on different machines (one in my ubuntu and the other one in a virtual-machined ubuntu), the client which tries to connect to the server via hostname gets a
Error getHostEntry: Resource temporarily unavailable.
This is the server.c file:
#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <fcntl.h>
#include <sys/un.h>
#include <unistd.h>
#include <pthread.h>
#include <string.h>
#include <malloc.h>
#include <netdb.h>
void checkHostname(int);
void checkHostEntry(struct hostent*);
void checkIpBuffer(char*);
int main(int argc, char **argv) {
struct sockaddr_in socketAddress;
int socketDescriptor, clientDescriptor, nread;
char buffer[1000];
pthread_t threadId;
char hostbuffer[256];
char *IPbuffer;
struct hostent *hostEntry;
int hostname;
if((socketDescriptor = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
printf("Errore durante la creazione della socket\n");
exit(1);
}
socketAddress.sin_family = AF_INET;
socketAddress.sin_addr.s_addr = htonl(INADDR_ANY);
socketAddress.sin_port = htons(atoi(argv[1]));
if(bind(socketDescriptor, (struct sockaddr*) &socketAddress, sizeof(socketAddress)) != 0) {
printf("Errore di bind()\n");
close(socketDescriptor);
exit(1);
}
hostname = gethostname(hostbuffer, sizeof(hostbuffer));
checkHostname(hostname);
hostEntry = gethostbyname(hostbuffer);
checkHostEntry(hostEntry);
IPbuffer = inet_ntoa(*((struct in_addr*) hostEntry->h_addr_list[0]));
printf("Hostname - %s\n", hostbuffer);
printf("Host IP - %s:%d\n", IPbuffer, ntohs(socketAddress.sin_port));
if(listen(socketDescriptor, 100) < 0) {
printf("Errore di listen()\n");
close(socketDescriptor);
exit(1);
}
return 0;
}
void checkHostname(int hostname) {
if (hostname == -1) {
perror("Errore gethostname");
exit(1);
}
}
void checkHostEntry(struct hostent *hostentry) {
if (hostentry == NULL) {
perror("Errore getHostEntry");
exit(1);
}
}
void checkIpBuffer(char *ip) {
if (ip == NULL) {
perror("Errore inet_ntoa");
exit(1);
}
}
And this is my client.c file
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <time.h>
#include <signal.h>
#include <string.h>
#include <pthread.h>
#include <netdb.h>
int main(int argc, char **argv) {
struct sockaddr_in clientAddress;
int choice, nread, serverIp;
char *IPbuffer;
struct hostent *host_entry;
if((clientDescriptor = socket(PF_INET, SOCK_STREAM, 0)) < 0) {
printf("Errore nella creaione del socket\n");
exit(1);
}
host_entry = gethostbyname(argv[1]);
checkHostEntry(host_entry)
IPbuffer = inet_ntoa(*((struct in_addr*) host_entry->h_addr_list[0]));
clientAddress.sin_family = AF_INET;
clientAddress.sin_addr.s_addr = inet_addr(IPbuffer); // indirizzo IP
clientAddress.sin_port = htons(atoi(argv[2])); // porta
if(connect(clientDescriptor, (struct sockaddr*) &clientAddress, sizeof(clientAddress)) < 0) {
printf("Errore connect()\n");
close(clientDescriptor);
exit(1);
}
return 0;
}
void checkHostEntry(struct hostent *hostentry) {
if (hostentry == NULL) {
perror("Errore getHostEntry");
exit(1);
}
}
If I
./server.out 8888
it displays:
IP: 1.2.3.4
Hostname: johnmayer
and If i try to connect from another computer (with a ubuntu installed on a virtual box) to this server, using
./client johnmayer 8888
I sometimes get
Error getHostEntry: Resource temporarily unavailable.
Is there something wrong in the code?