Using 'abstract sockets' with AF_UNIX SOCK_DGRAM

Using 'abstract sockets' with AF_UNIX SOCK_DGRAM

I am trying to modify the original Michael Kerrisk AF_UNIX SOCK_DGRAM
sample client/server program (client, server) published in his book The
Linux Programming Interface, chapter 57. My goal is to replace the 'file
socket' definition with 'abstract socket' based on Kerrisk's example.
Unfortunately, I am not able to establish communication between my version
of the client and server. Of course, Kerrisk's version works with a flying
colors.
It is obvious to me, that I am doing something fundamentally wrong...
but... I could not figured out what it is.
Here is my version of the Kerrisk's code for server 'server':
int main(int argc, char *argv[])
{
struct sockaddr_un svaddr, claddr;
int sfd, j;
ssize_t numBytes;
socklen_t len;
char buf[BUF_SIZE];
char *abstract_server;
sfd = socket(AF_UNIX, SOCK_DGRAM, 0); /* Create server socket */
if (sfd == -1)
errExit("socket");
abstract_server = "viper_server";
/* Construct well-known address and bind server socket to it */
if (remove(abstract_server) == -1 && errno != ENOENT)
errExit("remove-%s", abstract_server);
memset(&svaddr, 0, sizeof(struct sockaddr_un));
svaddr.sun_family = AF_UNIX;
strncpy(&svaddr.sun_path[1], abstract_server, strlen(abstract_server));
if (bind(sfd, (struct sockaddr *) &svaddr,
sizeof(sa_family_t) + strlen(abstract_server) + 1) == -1)
errExit("bind");
/* Receive messages, convert to uppercase, and return to client */
for (;;) {
len = sizeof(struct sockaddr_un);
numBytes = recvfrom(sfd, buf, BUF_SIZE, 0,
(struct sockaddr *) &claddr, &len);
if (numBytes == -1)
errExit("recvfrom");
printf("Server received %ld bytes from %s\n", (long) numBytes,
claddr.sun_path);
for (j = 0; j < numBytes; j++)
buf[j] = toupper((unsigned char) buf[j]);
if (sendto(sfd, buf, numBytes, 0, (struct sockaddr *) &claddr, len)
!= numBytes)
fatal("sendto");
}
}
This is my version of the Kerrisk's code for the 'client':
int main(int argc, char *argv[])
{
struct sockaddr_un svaddr, claddr;
int sfd, j;
size_t msgLen;
ssize_t numBytes;
char resp[BUF_SIZE];
char *abstract_client;
char *abstract_server;
if (argc < 2 || strcmp(argv[1], "--help") == 0)
usageErr("%s msg...\n", argv[0]);
/* Create client socket; bind to unique pathname (based on PID) */
sfd = socket(AF_UNIX, SOCK_DGRAM, 0);
if (sfd == -1)
errExit("socket");
abstract_client = "viper_client";
abstract_server = "viper_server";
memset(&claddr, 0, sizeof(struct sockaddr_un));
claddr.sun_family = AF_UNIX;
strncpy(&claddr.sun_path[1], abstract_client, strlen(abstract_client));
if (bind(sfd, (struct sockaddr *) &claddr,
sizeof(sa_family_t) + strlen(abstract_client) + 1) == -1)
errExit("bind");
/* Construct address of server */
memset(&svaddr, 0, sizeof(struct sockaddr_un));
svaddr.sun_family = AF_UNIX;
strncpy(&svaddr.sun_path[1], abstract_server, strlen(abstract_server));
/* Send messages to server; echo responses on stdout */
for (j = 1; j < argc; j++) {
msgLen = strlen(argv[j]); /* May be longer than BUF_SIZE */
if (sendto(sfd, argv[j], msgLen, 0, (struct sockaddr *) &svaddr,
sizeof(struct sockaddr_un)) != msgLen)
{
fatal("sendto");
}
numBytes = recvfrom(sfd, resp, BUF_SIZE, 0, NULL, NULL);
/* Or equivalently: numBytes = recv(sfd, resp, BUF_SIZE, 0);
or: numBytes = read(sfd, resp, BUF_SIZE); */
if (numBytes == -1)
errExit("recvfrom");
printf("Response %d: %.*s\n", j, (int) numBytes, resp);
}
remove(claddr.sun_path); /* Remove client socket pathname */
exit(EXIT_SUCCESS);
}
How I am launching the test:
> ./server &
> ./client aa bb cc
> result: ERROR: sendto
Any help | suggestion | solution | RTFM is very welcome
Igor
P.S. Since my reputation is less than 10, I can post ONLY 2 links (see
Kerrisk's client URL, Kerrrisk's server URL at the top of this post). So,
I did a "cut&paste" the Kerrisk's code/example for "How to use abstract
sockets".
int main(int argc, char *argv[])
{
int sockfd;
struct sockaddr_un addr;
char *str;
memset(&addr, 0, sizeof(struct sockaddr_un)); /* Clear address
structure */
addr.sun_family = AF_UNIX; /* UNIX domain address */
/* addr.sun_path[0] has already been set to 0 by memset() */
str = "xyz"; /* Abstract name is "\0abc" */
strncpy(&addr.sun_path[1], str, strlen(str));
// In early printings of the book, the above two lines were instead:
//
// strncpy(&addr.sun_path[1], "xyz", sizeof(addr.sun_path) - 2);
// /* Abstract name is "xyz" followed by null bytes */
sockfd = socket(AF_UNIX, SOCK_STREAM, 0);
if (sockfd == -1)
errExit("socket");
if (bind(sockfd, (struct sockaddr *) &addr,
sizeof(sa_family_t) + strlen(str) + 1) == -1)
errExit("bind");
// In early printings of the book, the final part of the bind() call
// above was instead:
// sizeof(struct sockaddr_un)) == -1)
sleep(60);
exit(EXIT_SUCCESS);
}