socket programming

[bkouhi]

Hi.

Here is my code:

int
main(int argc, char *argv[])
{

        int sockfd;

        unsigned short port = 1234;

        char *address = "127.0.0.1";
        char message[BUFSIZ];

        struct sockaddr_in connection;

        if( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
        {
                printf("socket error\n");
                exit(EXIT_FAILURE);
        }

        connection.sin_addr.s_addr = inet_addr(address);
        connection.sin_port = htons(port);
        connection.sin_family = AF_INET;
        memset( &(connection.sin_zero), '\0', 8 );

        if( (connect(sockfd, (struct sockaddr*)&connection, sizeof(struct sockaddr))) == -1);
        {
                printf("connect error\n");
                exit(EXIT_FAILURE);
        }

        for(;;)
        {
                scanf("%s", &message);
                send(sockfd, message, sizeof(message), 0);
        }

        close(sockfd);

        return 0;
}

In one terminal:
nc -k -l 127.0.0.1 1234

And in another one:

[CMD]./a.out[/CMD]
connect error

What's wrong with this code?

 

[Anonymous]

int main(int argc, char *argv[])
{
       int sockfd;

        unsigned short port = 1234;

        char *address = "127.0.0.1";
        char message[BUFSIZ];

        struct sockaddr_in connection;

        if( (sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1)
        {
                printf("socket error\n");
                exit(EXIT_FAILURE);
        }

        connection.sin_addr.s_addr = inet_addr(address);
        connection.sin_port = htons(port);
        connection.sin_family = AF_INET;
        memset( &(connection.sin_zero), '\0', 8 );

        if( (connect(sockfd, (struct sockaddr*)&connection, sizeof(struct [color="Red"]sockaddr[/color]))) == -1)[color="Red"][B];[/B][/color]
        {
                printf("connect error\n");
                exit(EXIT_FAILURE);
        }

        for(;;)
        {
                scanf("%s", [color="red"][B]&[/B][/color]message);
                send(sockfd, message, [color="Red"]sizeof[/color](message), 0);
        }

        close(sockfd);

        return 0;
}

...

What's wrong with this code?

The errors are marked with red color:

1. Replace sockaddr with sockaddr_in
2. Remove the semicolon at the end of the if() statement
3. Remove the address operator & in the scanf() statement
4. Replace sizeof() with strlen()

Best regards

Rolf

 

[nslay]

You might also find getaddrinfo(3) a better and more convenient way to set these structures up. For as general and powerful as sockets are, the whole type punning is just an awful mess ...

const char *address = "127.0.0.1";
const char *port = "1234";
struct addrinfo hints, *res = NULL;
int e;

memset(&hints, 0, sizeof(hints));

hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_protocol = IPPROTO_TCP;
hints.ai_flags = AI_NUMERICHOST; /* Just leave this as 0 if you want it to work in the general case of either an address or hostname */

e = getaddrinfo(address, port, &hints, &res);

if (e != 0) {
  fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(e));
  return -1;
}

if (connect(sockfd, res->ai_addr, res->ai_addrlen) == -1) {
  perror("connect");
  freeaddrinfo(res);
  return -1;
}

freeaddrinfo(res);

/* ... */

Hope this helps...