The code below is a chatroom. First I run the server, and then the clients. The clients reach the server with sockets. Then the server accepts the connection and the client has to enter his nickname.
I use threads because this way, the fgets is not blocking and multiple clients can reach the server even if a client is slow to enter his nickname.
Until here, there is no problem and everything works, even the select.
After this, the client can introduce a message which is send to all the clients (this is the principle of a chat :P). The problem is that from here, the select doesn't react and stay blocked. Maybe it's because of the FD_set or the threads but actually I don't know and that is the problem.
server.c:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <sys/wait.h>
#include <pthread.h>
#define MYPORT 5555
#define PSEUDO_MAX 30
#define MESSAGE_MAX 1000
#define BACKLOG 10
struct User {
char pseudo[PSEUDO_MAX];
int socket;
struct User *next;
};
struct Thread {
struct User* lst;
fd_set* readfds;
int* max;
int socket;
pthread_mutex_t* mutex;
};
void add(struct User** pp, const char *t, const int sock)
{
struct User *p = malloc(sizeof(*p));
strcpy(p->pseudo, t);
p->socket = sock;
p->next = NULL;
while (*pp)
pp = &(*pp)->next;
*pp = p;
}
void print(const struct User* n)
{
for ( ; n; n = n->next ){
printf("LISTE : %s\n", n->pseudo);
printf("LISTE : %d\n", n->socket);
}
printf("\n");
}
void *thread_pseudo(void *arg)
{
struct Thread* ps_thread = (struct Thread*)arg;
int nsock = ps_thread->socket;
struct User* lst = ps_thread->lst;
int* max = ps_thread->max;
pthread_mutex_t* mutex = ps_thread->mutex;
pthread_mutex_lock(mutex);
fd_set* readfds = ps_thread->readfds;
pthread_mutex_unlock(mutex);
char pseudo[PSEUDO_MAX];
if (send(nsock, "Bienvenue sur le chat !\n",24,0)==-1){
perror("Serveur: send");
}
if (recv(nsock, pseudo, PSEUDO_MAX, 0) == -1) {
perror("Serveur: recv 2: ");
}
pthread_mutex_lock(mutex);
FD_SET(nsock, readfds); // Ajout du nouveau socket au select
*max = (nsock < *max ? *max : nsock);
pthread_mutex_unlock(mutex);
add(&lst, pseudo, nsock);
print(lst);
pthread_exit(NULL);
}
int findSender(fd_set* readfds, const struct User* n){
int socket = 0;
for ( ; n; n = n->next ){
if(FD_ISSET(n->socket, readfds)){
socket = n->socket;
}
}
return socket;
}
int main()
{
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
int sockfd2, new_fd; // listen on sock_fd, new connection on new_fd
int max;
struct sockaddr_in my_addr; // my address information
struct sockaddr_in their_addr; // connector's address information
unsigned int sin_size;
int yes=1;
struct User *lst = NULL; // Initialisation de la liste des Users
struct Thread *ps_thread = malloc(sizeof(*ps_thread)); // Initialisation du struct qui contient les paramètres pour le thread
fd_set readfds;
if ((sockfd2 = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
perror("Serveur: socket 2");
return EXIT_FAILURE;
}
if (setsockopt(sockfd2,SOL_SOCKET,SO_REUSEADDR, &yes,sizeof(int)) == -1) {
perror("Serveur: setsockopt 2");
return EXIT_FAILURE;
}
my_addr.sin_family = AF_INET;
my_addr.sin_port = htons(MYPORT);
my_addr.sin_addr.s_addr = INADDR_ANY;
memset(&(my_addr.sin_zero), '\0', 8);
if (bind(sockfd2, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) {
perror("Serveur: bind 2");
return EXIT_FAILURE;
}
if (listen(sockfd2, BACKLOG) == -1) {
perror("Serveur: listen 2");
return EXIT_FAILURE;
}
//Initialisation du fd_set et du max
FD_ZERO(&readfds);
FD_SET(sockfd2, &readfds);
max = sockfd2;
while(1){
if (select(max+1, &readfds, NULL, NULL, NULL) < 0){
printf("error select\n");
}
int sock = findSender(&readfds, lst);
if(FD_ISSET(sockfd2, &readfds)){
new_fd = accept(sockfd2, (struct sockaddr *)&their_addr, &sin_size);
if (new_fd == -1) {
perror("Serveur: accept");
}
pthread_t thread;
ps_thread->lst = lst;
ps_thread->readfds = &readfds;
ps_thread->max = &max;
ps_thread->socket = new_fd;
ps_thread->mutex = &mutex;
if (pthread_create(&thread, NULL, thread_pseudo, ps_thread)) {
perror("pthread_create");
return EXIT_FAILURE;
}
}
else if(FD_ISSET(sock, &readfds)) {
char* message;
int sock = findSender(&readfds, lst);
if (recv(sock, message, MESSAGE_MAX, 0) == -1) {
perror("Serveur: recv 2: ");
}
}
else{
printf("ERROR\n");
}
}
return EXIT_SUCCESS;
}
client.c:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <pthread.h>
#define PORT 5555
#define PSEUDO_MAX 30
#define MESSAGE_MAX 1000
void getPseudo(char* pseudo) {
size_t ln = -1;
while (ln <= 0 || ln > PSEUDO_MAX-1) {
printf("Entrez votre pseudo : ");
fgets(pseudo, PSEUDO_MAX, stdin);
ln = strlen(pseudo) - 1;
}
if (pseudo[ln] == '\n')
pseudo[ln] = '\0';
}
void getMessage(char* message) {
size_t ln = -1;
while (ln <= 0 || ln > MESSAGE_MAX-1) {
printf(">");
fgets(message, MESSAGE_MAX, stdin);
ln = strlen(message) - 1;
}
if (message[ln] == '\n')
message[ln] = '\0';
}
void *thread_message(void *arg)
{
printf("Bonjour\n");
char* message;
message = malloc (sizeof(char) * MESSAGE_MAX);
int* sockfd = (int*)arg;
printf("%d\n", *sockfd);
while (1) {
getMessage(message);
if (send(*sockfd, message, strlen(message), 0) == -1){
perror("Client: send message");
}
}
pthread_exit(NULL);
}
int main(int argc, char *argv[])
{
int sockfd, numbytes;
struct sockaddr_in their_addr;
// connector's address information
struct hostent *he;
char buf[MESSAGE_MAX];
long int term1, term2, res;
int demande_pseudo = 0;
char* pseudo;
pseudo = malloc (sizeof(char) * PSEUDO_MAX);
if (argc != 2) {
fprintf(stderr, "Donner le nom du serveur.");
return EXIT_FAILURE;
}
if ((he=gethostbyname(argv[1])) == NULL) {
perror("Client: gethostbyname");
return EXIT_FAILURE;
}
if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
perror("Client: socket");
return EXIT_FAILURE;
}
their_addr.sin_family = AF_INET;
their_addr.sin_port = htons(PORT);
their_addr.sin_addr = *((struct in_addr*)he->h_addr);
memset(&(their_addr.sin_zero), '\0', 8);
if (connect(sockfd, (struct sockaddr *)&their_addr, sizeof(struct sockaddr)) == -1) {
perror("Client: connect");
return EXIT_FAILURE;
}
while (1) {
if ((numbytes=recv(sockfd, buf, MESSAGE_MAX-1, 0)) == -1) {
perror("Client: recv");
return EXIT_FAILURE;
}
if (demande_pseudo == 0) {
buf[numbytes] = '\0';
printf("%s",buf);
getPseudo(pseudo);
printf("Tu as choisi comme pseudo : %s\n", pseudo);
demande_pseudo++;
printf("%d\n", sockfd);
if (send(sockfd, pseudo, strlen(pseudo), 0) == -1){
perror("Client: send pseudo");
return EXIT_FAILURE;
}
pthread_t thread;
if (pthread_create(&thread, NULL, thread_message, &sockfd)) {
perror("pthread_create");
return EXIT_FAILURE;
}
}
else
{
}
}
close(sockfd);
return EXIT_SUCCESS;
}
First, your question is confusing, try to be more specific giving some examples. If I understood your question, your problem is that your select is configured to operate on blocking mode. This is an example on how to set your socket flags to non-blocking mode.
flags = fcntl(sock, F_GETFL, 0);
if(flags < 0)
err(1, "%s: fcntl", __FUNCTION__);
ret = fcntl(sock, F_SETFL, flags | O_NONBLOCK);
if(ret < 0)
err(1, "%s: fcntl:", __FUNCTION__);
Well, one of your problems is that your main function doesn't wait your thread update readfds
and max
, thus getting blocked on select with the wrong values for those variables. You could solve that by either adding pthread_join(thread, NULL);
after you create your thread OR , as I said first, setting your select as non-blocking mode.
pthread_join
) you'll not be able to process incoming
requests while waiting for your thread to finish,hence invalidating the whole purpose of having threads: being available to process incoming requests.Try to develop those ideas and you'll make that code work! (: