Problems when debugging a socket-using program in C: connect
I'm writting a simple client-server system using unix sockets. When executed from a terminal, my Client program creats a segmentation fault.
I'm quite sure that seg-fault is caused by some noob error, but my problem comes when I try to debug it using KDBG (kde gdb frontend).
This is where it breaks:
if (DEBUG) printf("-- connect()... \n");
if (connect (mySocket, (struct sockaddr *)socketAddr,sizeof (*socketAddr)) == -1) {
perror(error);
printf("%s\n",error);
printf ("-- Error when stablishing a connection\n");
return -1;
}
开发者_StackOverflow
And this is the output:
-- connect()...
Connection refused
-- Error when stablishing a connection
Can't I debug this code that way? Why?
If I should can, do you now what's hapenning there? What should i do in order to get more information?
PS: PS: @abelenky: that part works perfect out of the debugger. This is the declaration of socketAddr:
struct sockaddr_in socketAddr;
...
if ( (mySocket = socket(AF_INET, SOCK_STREAM, 0)) == -1) {
printf("Error al crear el socket\n");
return -2;
}
These functions expect a string and you are passing them something else.
For example:
perror("socket");
Although I don't know from your code where error
is declared... Perhaps you are thinking of the global variable errno
, which is in integer?
By the way, perror
is roughly equivalent to this:
void perror(const char *str)
{
fprintf(stderr, "%s: %s\n", str, strerror(errno));
}
Update based on comments:
In that case my guess is you haven't intiailized error
to anything... I am not sure what you are expecting to be in error
, but for example you might want to try something:
snprintf(error, sizeof(error), "Error in %s:%d\n", __FILE__, __LINE__);
perror(error);
Update 2:
I think you want this:
if (connect (mySocket, (struct sockaddr *)&socketAddr, sizeof (socketAddr)) == -1) {
Note that I have added a &
before socketAddr
and removed the *
from the sizeof
.
How are you doing hostname lookups? I recommend getaddrinfo
, eg.:
struct addrinfo *res = NULL, hint;
char service[32];
int error;
snprintf(service, sizeof(service), "%d", port);
memset(&hint, 0, sizeof(hint));
hint.ai_socktype = SOCK_STREAM;
if ((error = getaddrinfo(host, service, &hint, &res)))
{
fprintf(stderr, "No se pudo encontrar %s: %s\n", host, gai_strerror(error));
}
else
{
fd = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
if (fd < 0)
{
perror("Error al crear el socket");
}
else if (connect(fd, res->ai_addr, res->ai_addrlen))
{
perror("Error al conexionar con el servidor");
close(fd);
fd = -1;
}
}
if (res)
{
freeaddrinfo(res);
}
This will let you get a sockaddr
from a hostname and port without caring about IPv4, IPv6, etc.
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