Added epoll-based socket manager (not tested).

Makefile

@@ -22,6 +22,7 @@ OBJS = $(addprefix $(OBJ_DIR)/, $(addsuffix .o, $(basename $(notdir $(SRC_FILES)
 
 CC = gcc
 CFLAGS += -Wall -std=c99
+LDFLAGS += -lpthread
 
 all:cuckoo-hash
 

socket-manager.c

+#include "common.h"
+#include "socket-manager.h"
+
+#include <sys/socket.h>
+#include <netinet/in.h>
+#include <errno.h>
+#include <pthread.h>
+#include <err.h>
+#include <fcntl.h>
+#include <sys/epoll.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+static const uint BUFF_SIZE = 4096;
+
+/*----------------------------------------------------------------------------*/
+
+sm_manager *sm_create( short port, uint thr_count,
+                       void (*answer_fnc)( const char *, uint, char *, uint ) )
+{
+    sm_manager *manager = malloc(sizeof(sm_manager));
+
+    manager->socket = socket( AF_INET, SOCK_DGRAM, 0 );
+    if (manager->socket == -1) {
+        fprintf(stderr, "ERROR: %d: %s.\n", errno, strerror(errno));
+        free(manager);
+        return NULL;
+    }
+
+    struct sockaddr_in addr;
+
+    addr.sin_family = AF_INET;
+    addr.sin_port = htons( port );
+    addr.sin_addr.s_addr = htonl( INADDR_ANY );
+
+    // Set non-blocking mode on the socket
+    int old_flag = fcntl(manager->socket, F_GETFL, 0);
+    if (fcntl(manager->socket, F_SETFL, old_flag | O_NONBLOCK) == -1) {
+        free(manager);
+        err(1, "fcntl");
+    }
+
+    int res = bind( manager->socket, (struct sockaddr *)&addr, sizeof(addr) );
+    if (res == -1) {
+        printf( "ERROR: %d: %s.\n", errno, strerror(errno) );
+        free(manager);
+        return NULL;
+    }
+
+    manager->epfd = epoll_create(1);
+
+    manager->event.events = EPOLLIN | EPOLLPRI | EPOLLERR | EPOLLHUP;
+    manager->event.data.fd = manager->socket;
+    if ((res = epoll_ctl(manager->epfd, EPOLL_CTL_ADD, manager->socket,
+                         &manager->event))
+        != 0) {
+        printf( "ERROR: %d: %s.\n", errno, strerror(errno) );
+        free(manager);
+        return NULL;
+    }
+
+    //printf("Creating mutex\n");
+    int errval;
+    if ((errval = pthread_mutex_init(&manager->mutex, NULL)) != 0) {
+        printf( "ERROR: %d: %s.\n", errval, strerror(errval) );
+        free(manager);
+        return NULL;
+    } /*else {
+        printf("Successful\n");
+    }*/
+
+    manager->thread_count = thr_count;
+    manager->answer_fnc = answer_fnc;
+
+    return manager;
+}
+
+/*----------------------------------------------------------------------------*/
+
+void sm_destroy( sm_manager *manager )
+{
+    close(manager->socket);
+    free(manager);
+}
+
+/*----------------------------------------------------------------------------*/
+
+void *sm_listen( void *obj )
+{
+    sm_manager *manager = (sm_manager *)obj;
+    char buf[BUFF_SIZE];
+    struct sockaddr_in faddr;
+    int addrsize = sizeof(faddr);
+    int n, i ,fd;
+    char answer[BUFF_SIZE];
+    uint answer_size = 0;
+
+    while (1) {
+        int nfds = epoll_wait(manager->epfd, &manager->event, 1, -1);
+        if (nfds < 0)
+            err(1, "epoll_wait");
+
+        // for each ready socket
+        for(i = 0; i < nfds; i++) {
+            //printf("locking mutex from thread %ld\n", pthread_self());
+            pthread_mutex_lock(&manager->mutex);
+            fd = manager->event.data.fd;
+
+            if ((n = recvfrom(fd, buf, BUFF_SIZE, 0, (struct sockaddr *)&faddr,
+                             (socklen_t *)&addrsize)) > 0) {
+
+                //printf("unlocking mutex from thread %ld\n", pthread_self());
+                pthread_mutex_unlock(&manager->mutex);
+
+                manager->answer_fnc(buf, n, answer, answer_size);
+
+                int sent = sendto(fd, answer, answer_size, MSG_DONTWAIT,
+                                  (struct sockaddr *)&faddr,
+                                  (socklen_t)addrsize);
+
+                if (sent < 0) {
+                    const int error = errno;
+                    printf( "Error sending: %d, %s.\n", error, strerror(error) );
+                }
+            } else {
+                pthread_mutex_unlock(&manager->mutex);
+            }
+        }
+    }
+
+}
+
+/*----------------------------------------------------------------------------*/
+
+int sm_start( sm_manager *manager )
+{
+    pthread_t threads[manager->thread_count];
+
+    int i;
+
+    for (i = 0; i < manager->thread_count; ++i)
+    {
+        if (pthread_create(&threads[i], NULL, sm_listen, (void *)manager))
+        {
+            printf( "ERROR CREATING THREAD %d", i );
+            return -1;
+        }
+    }
+    for (i = 0; i < manager->thread_count; ++i)
+    {
+        if ( pthread_join( threads[i], NULL ) )
+        {
+            printf( "ERROR JOINING THREAD %d", i );
+            return -1;
+        }
+    }
+
+    return 0;
+}

socket-manager.h

+#ifndef SOCKET_MANAGER
+#define SOCKET_MANAGER
+
+#include <sys/epoll.h>
+#include <pthread.h>
+#include "common.h"
+
+/*----------------------------------------------------------------------------*/
+
+struct sm_manager {
+    int socket;         // later use array of sockets?
+    uint thread_count;
+    struct epoll_event event;
+    int epfd;
+    void (*answer_fnc)( const char *, uint, char *, uint );
+    pthread_mutex_t mutex;
+};
+
+typedef struct sm_manager sm_manager;
+
+/*----------------------------------------------------------------------------*/
+
+sm_manager *sm_create( short port, uint thr_count,
+                       void (*answer_fnc)( const char *, uint, char *, uint ) );
+
+void sm_destroy( sm_manager *manager );
+
+int sm_start( sm_manager *manager );
+
+#endif