CODEWITHSUNDEEP
clinuxsockets
0poss
0poss

Reputation: 173

C socket programming errors

It's been an hour since I started looking for THE error. I just started C sockets. The program exits with code -1 after printing "Error 1 connection error". The server in online, it's a netcat server. Where did I messed up ?

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

#define HOST "127.0.0.1"
#define PORT 4444

int main(int argc, const char *argv[])
{
    struct sockaddr_in addr;
    int sock = 0;
    int ret;
    struct sockaddr_in server_addr;
    char *msg = "Hello world !\n";
    char inBuffer[1024] = { 0 };
    if (sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) < 0)
    {
        printf("Error %d socket creating.\n", sock);
        exit(-1);
    }
    else
    {
        memset(&server_addr, '0', sizeof(server_addr));

        server_addr.sin_family = AF_INET;
        server_addr.sin_port = htons(PORT);
        if (ret = inet_pton(AF_INET, HOST, &server_addr.sin_addr) <= 0)
        {
            printf("Error %d unsuported address: %d\n", ret);
            exit(-2);
        }
        else
        {
            if (ret = connect(sock, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0)
            {
                printf("Error %d connection error\n", ret);
                exit(-3);
            }
            else
            {
                send(sock, msg, strlen(msg), 0);
                read(sock, inBuffer, 1024);
                printf("%s\n", inBuffer);
                return 0;
            }
        }
    }



}

Upvotes: 0

Views: 712

Answers (1)

Some programmer dude
Some programmer dude

Reputation: 409472

Due to operator precedence, the expression

sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) < 0

is actually equal to

sock = (socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) < 0)

That is, you assign the result of the comparison socket(AF_INET, SOCK_STREAM, IPPROTO_TCP) < 0 to the variable sock. The result of that comparison will always be either 0 (for false) or 1 (for true). Neither 0 nor 1 should be a valid socket.

You need to explicitly add parentheses for the assignment:

(sock = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0

The same needs to be done for the connect call and the comparison there.

Upvotes: 2

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