C Programming Sockets.

[Gaweph]

I cerated a simple server.c program in class. it worked fine.

When compiling i had to do gcc server.c -o server -lsocket. It worked fine on the Sun Microsystems in the class.

When i got home i tried to compile the same program on Ubuntu. When compiling i get the following error:

gcc server.c -o server
server.c: In function ‘main’:
server.c:11: error: storage size of ‘servaddr’ isn’t known
server.c:11: error: storage size of ‘cliaddr’ isn’t known
server.c:15: warning: incompatible implicit declaration of built-in function ‘bzero’
server.c:17: error: ‘INADDR_ANY’ undeclared (first use in this function)
server.c:17: error: (Each undeclared identifier is reported only once
server.c:17: error: for each function it appears in.)

Any help would be appreciated (I also tried to do gcc server.c -o server -lsocket, with the same errors.

[redhead]

I would like to know what kind of source code you're using, since on Linux any socket using program that includes netinet/in.h and sys/socket.h will be able to compile without any linker flags.
Considder these two small programs:

Listener:

/*
** listener.c -- a datagram sockets "server" demo
*/

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>

#define MYPORT 4950    /* the port users will be connecting to */

#define MAXBUFLEN 100

main()
{
    int sockfd;
    struct sockaddr_in my_addr;    /* my address information */
    struct sockaddr_in their_addr; /* connector's address information */
    int addr_len, numbytes;
    char buf[MAXBUFLEN];

    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
        perror("socket");
        exit(1);
    }

    my_addr.sin_family = AF_INET;         /* host byte order */
    my_addr.sin_port = htons(MYPORT);     /* short, network byte order */
    my_addr.sin_addr.s_addr = INADDR_ANY; /* automatically fill with my IP */
    bzero(&(my_addr.sin_zero), 8);        /* zero the rest of the struct */

    if (bind(sockfd, (struct sockaddr *)&my_addr, sizeof(struct sockaddr)) == -1) {
        perror("bind");
        exit(1);
    }

    addr_len = sizeof(struct sockaddr);
    if ((numbytes=recvfrom(sockfd,buf,MAXBUFLEN,0,(struct sockaddr *)&their_addr, &addr_len)) == -1) {
        perror("recvfrom");
        exit(1);
    }

    printf("got packet from %s\n",inet_ntoa(their_addr.sin_addr));
    printf("packet is %d bytes long\n",numbytes);
    buf[numbytes] = '\0';
    printf("packet contains \"%s\"\n",buf);

    close(sockfd);
}

talker:

/*
** talker.c -- a datagram "client" demo
*/

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#include <sys/socket.h>
#include <sys/wait.h>

#define MYPORT 4950    /* the port users will be connecting to */

int main(int argc, char *argv[])
{
    int sockfd;
    struct sockaddr_in their_addr; /* connector's address information */
    struct hostent *he;
    int numbytes;

    if (argc != 3) {
        fprintf(stderr,"usage: talker hostname message\n");
        exit(1);
    }

    if ((he=gethostbyname(argv[1])) == NULL) {  /* get the host info */
        perror("gethostbyname");
        exit(1);
    }

    if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
        perror("socket");
        exit(1);
    }

    their_addr.sin_family = AF_INET;         /* host byte order */
    their_addr.sin_port = htons(MYPORT);     /* short, network byte order */
    their_addr.sin_addr = *((struct in_addr *)he->h_addr);
    bzero(&(their_addr.sin_zero), 8);        /* zero the rest of the struct */

    if ((numbytes=sendto(sockfd,argv[2],strlen(argv[2]),0,(struct sockaddr *)&their_addr, sizeof(struct sockaddr))) == -1) {
        perror("recvfrom");
        exit(1);
    }
    printf("sent %d bytes to %s\n", numbytes, inet_ntoa(their_addr.sin_addr));
    close(sockfd);

    return 0;
}

Which can easily be compiled with
~ > gcc -o program file.c

[Gaweph]

Thanx for that. I just needed to add #include <netinet/in.h>

Is now working great.

Thanx again