diff --git a/drop/pass-socket_client.c b/drop/pass-socket_client.c
new file mode 100644
index 0000000..1b96401
--- /dev/null
+++ b/drop/pass-socket_client.c
@@ -0,0 +1,270 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <netinet/in.h>
+#include <sys/stat.h>
+#include <arpa/inet.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <time.h>
+#include <errno.h>
+#include <assert.h>
+#include <stdarg.h>
+
+#define USOCK                               "./.socket"
+
+#define handle_error(msg) \
+    do { log_error (msg); exit(EXIT_FAILURE); } while (0)
+
+#define handle_err(fun,msg)\
+    do { log_error ("%s: file %s line %d %s", fun, __FILE__, __LINE__, msg); } while (0)
+
+void log_format (const char* tag, const char* message, va_list args) {
+    time_t now;
+
+    time(&now);
+
+    char * date =ctime(&now);
+    date[strlen(date) - 1] = '\0';
+    printf("%s:%s: ", date, tag);
+    vprintf(message, args);
+
+    printf("\n");
+}
+
+void log_error (const char* message, ...) {
+    va_list args;
+    va_start(args, message);
+
+    log_format("error", message, args);
+
+    va_end(args);
+}
+
+void log_info (const char* message, ...) {
+    va_list args;
+    va_start(args, message);
+
+    log_format("info", message, args);
+    va_end(args);
+}
+
+void log_debug (const char* message, ...) {
+    va_list args;
+    va_start(args, message);
+
+    log_format("debug", message, args);
+
+    va_end(args);
+}
+
+static
+int recvsockfd (int socket)  // receive fd from socket
+{
+    struct msghdr msg = {0};
+
+    /* On Mac OS X, the struct iovec is needed, even if it points to minimal data */
+    char m_buffer[1];
+    struct iovec io = { .iov_base = m_buffer, .iov_len = sizeof(m_buffer) };
+    msg.msg_iov = &io;
+    msg.msg_iovlen = 1;
+
+    char c_buffer[256];
+    msg.msg_control = c_buffer;
+    msg.msg_controllen = sizeof(c_buffer);
+
+    if (recvmsg(socket, &msg, 0) < 0)
+        handle_err ("recvsockfd", "Failed to receive message\n");
+
+    struct cmsghdr *cmsg = CMSG_FIRSTHDR(&msg);
+
+    printf ("About to extract fd\n");
+    int fd;
+    memmove(&fd, CMSG_DATA(cmsg), sizeof(fd));
+    printf ("Extracted fd %d\n", fd);
+
+    return fd;
+}
+
+int usock_connect (int *fd, const char *path)
+{
+    assert (fd != NULL);
+    assert (path != NULL);
+
+    if (fd == NULL) {
+        handle_err ("usock_connect", "fd == NULL");
+        return -1;
+    }
+
+    if (path == NULL) {
+        handle_err ("usock_connect", "path == NULL");
+        return -1;
+    }
+
+    int sfd;
+    struct sockaddr_un my_addr;
+    socklen_t peer_addr_size;
+
+    sfd = socket (AF_UNIX, SOCK_STREAM, 0);
+    if (sfd == -1) {
+        handle_err ("usock_connect", "sfd == -1");
+        return -1;
+    }
+
+    // clear structure 
+    memset(&my_addr, 0, sizeof(struct sockaddr_un));
+
+    my_addr.sun_family = AF_UNIX;
+    strncpy(my_addr.sun_path, path, strlen (path));
+
+    peer_addr_size = sizeof(struct sockaddr_un);
+    if(connect(sfd, (struct sockaddr *) &my_addr, peer_addr_size) == -1) {
+        handle_err ("usock_connect", "connect == -1");
+        perror("connect()");
+        exit(errno);
+    }
+
+    *fd = sfd;
+
+    return 0;
+}
+
+int usock_init (int *fd, const char *path)
+{
+    assert (fd != NULL);
+    assert (path != NULL);
+
+    if (fd == NULL) {
+        handle_err ("usock_init", "fd == NULL");
+        return -1;
+    }
+
+    if (path == NULL) {
+        handle_err ("usock_init", "path == NULL");
+        return -1;
+    }
+
+    int sfd;
+    struct sockaddr_un my_addr;
+    socklen_t peer_addr_size;
+
+    sfd = socket (AF_UNIX, SOCK_STREAM, 0);
+    if (sfd == -1) {
+        handle_err ("usock_init", "sfd == -1");
+        return -1;
+    }
+
+    // clear structure 
+    memset(&my_addr, 0, sizeof(struct sockaddr_un));
+
+    my_addr.sun_family = AF_UNIX;
+    strncpy(my_addr.sun_path, path, strlen (path));
+
+    // TODO FIXME
+    // delete the unix socket if already created
+
+    peer_addr_size = sizeof(struct sockaddr_un);
+
+    if (bind (sfd, (struct sockaddr *) &my_addr, peer_addr_size) == -1) {
+        handle_err ("usock_init", "bind == -1");
+        perror("bind()");
+        return -1;
+    }
+
+    if (listen (sfd, 5) == -1) {
+        handle_err ("usock_init", "listen == -1");
+        perror("listen()");
+        return -1;
+    }
+
+    *fd = sfd;
+
+    return 0;
+}
+
+int usock_accept (int fd, int *pfd)
+{
+    assert (pfd != NULL);
+
+    if (pfd == NULL) {
+        handle_err ("usock_accept", "pfd == NULL");
+        return -1;
+    }
+
+    struct sockaddr_un peer_addr;
+    memset (&peer_addr, 0, sizeof (struct sockaddr_un));
+    socklen_t peer_addr_size = 0;
+
+    *pfd = accept (fd, (struct sockaddr *) &peer_addr, &peer_addr_size);
+    if (*pfd < 0) {
+        handle_err ("usock_accept", "accept < 0");
+        perror("listen()");
+        return -1;
+    }
+
+    return 0;
+}
+
+int usock_close (int fd)
+{
+    int ret;
+    ret = close (fd);
+    if (ret < 0) {
+        handle_err ("usock_close", "close ret < 0");
+        perror ("closing");
+    }
+    return ret;
+}
+
+int usock_remove (const char *path)
+{
+    return unlink (path);
+}
+
+int main(int argc, char * argv[])
+{
+    int tcpsockfd;
+    int usockfd;
+    // check the number of args on command line
+    if(argc != 1)
+    {
+        fprintf (stderr, "USAGE: %s\n", argv[0]);
+        exit(EXIT_FAILURE);
+    }
+
+    printf("Connection to the unix socket\n");
+
+    // 1. unix socket connection
+    int ret = usock_connect (&usockfd, USOCK);
+    if (ret != 0) {
+        fprintf (stderr, "error: usock_connect\n");
+        exit(EXIT_FAILURE);
+    }
+
+    printf("Receiving the tcp socket\n");
+
+    // 2. receive the tcp socket
+    tcpsockfd = recvsockfd (usockfd);
+
+    printf("Sending 'hello world' to the tcp socket\n");
+
+    // 3. send a message to check the connection is effective
+    if (write(tcpsockfd, "hello world\n", strlen("hello world\n")) == -1) {
+        perror("write");
+        close(tcpsockfd);
+        exit(EXIT_FAILURE);
+    }
+
+    printf("Disconnection of both sockets\n");
+
+    // 4. close sockets
+    close(usockfd);
+    close(tcpsockfd);
+
+    return EXIT_SUCCESS;
+}
diff --git a/drop/pass-socket_server.c b/drop/pass-socket_server.c
new file mode 100644
index 0000000..fc35280
--- /dev/null
+++ b/drop/pass-socket_server.c
@@ -0,0 +1,322 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#include <sys/socket.h>
+#include <sys/types.h>
+#include <sys/un.h>
+#include <netinet/in.h>
+#include <sys/stat.h>
+#include <arpa/inet.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+#include <time.h>
+#include <errno.h>
+#include <assert.h>
+#include <stdarg.h>
+
+#define USOCK                               "./.socket"
+
+#define handle_error(msg) \
+    do { log_error (msg); exit(EXIT_FAILURE); } while (0)
+
+#define handle_err(fun,msg)\
+    do { log_error ("%s: file %s line %d %s", fun, __FILE__, __LINE__, msg); } while (0)
+
+void log_format (const char* tag, const char* message, va_list args) {
+    time_t now;
+
+    time(&now);
+
+    char * date =ctime(&now);
+    date[strlen(date) - 1] = '\0';
+    printf("%s:%s: ", date, tag);
+    vprintf(message, args);
+
+    printf("\n");
+}
+
+void log_error (const char* message, ...) {
+    va_list args;
+    va_start(args, message);
+
+    log_format("error", message, args);
+
+    va_end(args);
+}
+
+void log_info (const char* message, ...) {
+    va_list args;
+    va_start(args, message);
+
+    log_format("info", message, args);
+    va_end(args);
+}
+
+void log_debug (const char* message, ...) {
+    va_list args;
+    va_start(args, message);
+
+    log_format("debug", message, args);
+
+    va_end(args);
+}
+
+int build_socket (char *servername, char * serverport)
+{
+    int sockfd;
+    struct sockaddr_in6 server;
+    socklen_t addrlen;
+
+    // socket factory
+    if((sockfd = socket(AF_INET6, SOCK_STREAM, IPPROTO_TCP)) == -1)
+    {
+        perror("socket");
+        exit(EXIT_FAILURE);
+    }
+
+    // init remote addr structure and other params
+    server.sin6_family = AF_INET6;
+    server.sin6_port   = htons(atoi(serverport));
+    addrlen           = sizeof(struct sockaddr_in6);
+
+    // get addr from command line and convert it
+    if(inet_pton(AF_INET6, servername, &server.sin6_addr) != 1)
+    {
+        perror("inet_pton");
+        close(sockfd);
+        exit(EXIT_FAILURE);
+    }
+
+    printf("Trying to connect to the remote host\n");
+    if(connect(sockfd, (struct sockaddr *) &server, addrlen) == -1)
+    {
+        perror("connect");
+        exit(EXIT_FAILURE);
+    }
+
+    return sockfd;
+}
+
+int usock_connect (int *fd, const char *path)
+{
+    assert (fd != NULL);
+    assert (path != NULL);
+
+    if (fd == NULL) {
+        handle_err ("usock_connect", "fd == NULL");
+        return -1;
+    }
+
+    if (path == NULL) {
+        handle_err ("usock_connect", "path == NULL");
+        return -1;
+    }
+
+    int sfd;
+    struct sockaddr_un my_addr;
+    socklen_t peer_addr_size;
+
+    sfd = socket (AF_UNIX, SOCK_STREAM, 0);
+    if (sfd == -1) {
+        handle_err ("usock_connect", "sfd == -1");
+        return -1;
+    }
+
+    // clear structure 
+    memset(&my_addr, 0, sizeof(struct sockaddr_un));
+
+    my_addr.sun_family = AF_UNIX;
+    strncpy(my_addr.sun_path, path, strlen (path));
+
+    peer_addr_size = sizeof(struct sockaddr_un);
+    if(connect(sfd, (struct sockaddr *) &my_addr, peer_addr_size) == -1) {
+        handle_err ("usock_connect", "connect == -1");
+        perror("connect()");
+        exit(errno);
+    }
+
+    *fd = sfd;
+
+    return 0;
+}
+
+int usock_init (int *fd, const char *path)
+{
+    assert (fd != NULL);
+    assert (path != NULL);
+
+    if (fd == NULL) {
+        handle_err ("usock_init", "fd == NULL");
+        return -1;
+    }
+
+    if (path == NULL) {
+        handle_err ("usock_init", "path == NULL");
+        return -1;
+    }
+
+    int sfd;
+    struct sockaddr_un my_addr;
+    socklen_t peer_addr_size;
+
+    sfd = socket (AF_UNIX, SOCK_STREAM, 0);
+    if (sfd == -1) {
+        handle_err ("usock_init", "sfd == -1");
+        return -1;
+    }
+
+    // clear structure 
+    memset(&my_addr, 0, sizeof(struct sockaddr_un));
+
+    my_addr.sun_family = AF_UNIX;
+    strncpy(my_addr.sun_path, path, strlen (path));
+
+    // TODO FIXME
+    // delete the unix socket if already created
+
+    peer_addr_size = sizeof(struct sockaddr_un);
+
+    if (bind (sfd, (struct sockaddr *) &my_addr, peer_addr_size) == -1) {
+        handle_err ("usock_init", "bind == -1");
+        perror("bind()");
+        return -1;
+    }
+
+    if (listen (sfd, 5) == -1) {
+        handle_err ("usock_init", "listen == -1");
+        perror("listen()");
+        return -1;
+    }
+
+    *fd = sfd;
+
+    return 0;
+}
+
+int usock_accept (int fd, int *pfd)
+{
+    assert (pfd != NULL);
+
+    if (pfd == NULL) {
+        handle_err ("usock_accept", "pfd == NULL");
+        return -1;
+    }
+
+    struct sockaddr_un peer_addr;
+    memset (&peer_addr, 0, sizeof (struct sockaddr_un));
+    socklen_t peer_addr_size = 0;
+
+    *pfd = accept (fd, (struct sockaddr *) &peer_addr, &peer_addr_size);
+    if (*pfd < 0) {
+        handle_err ("usock_accept", "accept < 0");
+        perror("listen()");
+        return -1;
+    }
+
+    return 0;
+}
+
+int usock_close (int fd)
+{
+    int ret;
+    ret = close (fd);
+    if (ret < 0) {
+        handle_err ("usock_close", "close ret < 0");
+        perror ("closing");
+    }
+    return ret;
+}
+
+int usock_remove (const char *path)
+{
+    return unlink (path);
+}
+
+int build_unix_socket (char * path)
+{
+    int remotefd, localfd;
+
+    usock_init (&localfd, path);
+    usock_accept (localfd, &remotefd);
+
+    return remotefd;
+}
+
+static
+void sendfd (int socket, int fd)  // send fd by socket
+{
+    struct msghdr msg = { 0 };
+    char buf[CMSG_SPACE(sizeof(fd))];
+    memset(buf, '\0', sizeof(buf));
+
+    /* On Mac OS X, the struct iovec is needed, even if it points to minimal data */
+    struct iovec io = { .iov_base = "", .iov_len = 1 };
+
+    msg.msg_iov = &io;
+    msg.msg_iovlen = 1;
+    msg.msg_control = buf;
+    msg.msg_controllen = sizeof(buf);
+
+    struct cmsghdr * cmsg = CMSG_FIRSTHDR(&msg);
+    cmsg->cmsg_level = SOL_SOCKET;
+    cmsg->cmsg_type = SCM_RIGHTS;
+    cmsg->cmsg_len = CMSG_LEN(sizeof(fd));
+
+    memmove(CMSG_DATA(cmsg), &fd, sizeof(fd));
+
+    msg.msg_controllen = cmsg->cmsg_len;
+
+    if (sendmsg(socket, &msg, 0) < 0)
+        handle_err("sendfd", "Failed to send message\n");
+}
+
+int main(int argc, char * argv[])
+{
+    // check the number of args on command line
+    if(argc != 3)
+    {
+        fprintf (stderr, "USAGE: %s @server port_num\n", argv[0]);
+        exit(EXIT_FAILURE);
+    }
+    char *servername = argv[1];
+    char *serverport = argv[2];
+
+    printf("Connection to the tcp socket\n");
+    // 1. socket creation (tcp), connection to the server
+    int sockfd = build_socket (servername, serverport);
+
+    printf("Sending 'coucou' to the tcp socket\n");
+    // send a message to check the connection is effective
+    if (write(sockfd, "coucou\n", strlen("coucou\n")) == -1) {
+        perror("write");
+        close(sockfd);
+        exit(EXIT_FAILURE);
+    }
+
+    printf ("Connection to the unix socket\n");
+    // 2. socket creation (unix)
+    int usockfd = build_unix_socket (USOCK);
+
+    printf ("Passing the tcp socket to the unix socket\n");
+    // 3. tcp socket passing to the client
+    sendfd (usockfd, sockfd);
+
+    // send a message to check the connection is (still) effective
+    if (write(sockfd, "bye\n", strlen("bye\n")) == -1) {
+        perror("write");
+        close(sockfd);
+        exit(EXIT_FAILURE);
+    }
+
+    printf("Disconnection\n");
+
+    // 4. close sockets
+    close(usockfd);
+    close(sockfd);
+
+    usock_remove (USOCK);
+
+    return EXIT_SUCCESS;
+}