0

I'm creating a server/client tcp connection in c which emulates an airline. I'm having problems sending the list of flights from the server to the client, I can only send a string of characters at the time, and the code I've implemented is not working, is giving me a segmentation fault, can someone please give me some inside into this?

This is the server, the send_all() function will take the socket id and the hashmap to send the list of flights line by line with the write() function. 

    int send_all(int socket, map_t flight_map)
    {
        struct hashmap_element {
            char* key;
            int in_use;
            any_t data;
        };

        struct hashmap_map {
            int table_size;
            int size;
            struct hashmap_element *data;
        };

        struct hashmap_map * map = (struct hashmap_map *) flight_map;

        //int index = map->tableSize;
        char line[12];
        int i = 0;
        for (i = 0; i < map->table_size; i++)
        {
            strcpy(line, return_flight(map->data[i].key, map->data[i].data));
            if (write(socket, line, strlen(line) + 1) < 0) {
                        error("error: writing to connection");
                        return 0;
            }
        }
        return 1;
    }
    char * return_flight(char * flight, void * seats) 
    {
        char tmp[20];
        strcpy(tmp, flight);
        strcat(tmp, (char *)seats);
        return tmp;
    }

Here is the Client side: the readSocket, is in charge of reading every single string passing trough the socket connection... 

// send input to server
        if (write(client_fd, command, strlen(command) + 1) < 0)
            error("error: writing to socket");

        printf("client: sending %s to server\n", command);

        // recieve response from server
        if (readSocket(client_fd, buffer) < 0)
            error("error: reading from socket");

        printf("client: read %s from server\n", buffer);

        printf("client: closing client\n");
        close(client_fd);
    }

    return 0;
}

static int readSocket(int socket, char *buffer)
{
     ssize_t bytes_read = 0;

     bytes_read = recv(socket, buffer, BUFSIZE - 1, 0);

     while (bytes_read > 0)
     {
         buffer[bytes_read] = 0; // Null-terminate the buffer
         printf("Buffer: %s\n", buffer);
         bytes_read = recv(socket, buffer, BUFSIZE - 1, 0);
     }
     if (bytes_read == -1)
     {
         fprintf("Socket recv failed: %s\n", strerror(errno));
         return -1;
     }
     return 0;
}
Isaac Reynaldo
  • 1
  • 1
    You're returning the address if an array that becomes non-existent the movement you return. This is undefined behaviour. – user207421 Jul 30 '17 at 00:48
  • As @EJP notes, you have `char * return_flight(char * flight, void * seats) { char tmp[20]; strcpy(tmp, flight); strcat(tmp, (char *)seats); return tmp; }` — that returns a pointer to a local array, which is UB. Don't do it. Manage the memory properly. – Jonathan Leffler Jul 30 '17 at 01:55
  • The *moment* you return, oops. – user207421 Jul 30 '17 at 03:35
  • Also, in the client, 'bytes_read = recv(socket, buffer, BUFSIZE - 1, 0);' in teh while loop needs to have its buffer addr and buffer length parameters updated each time to prevent overwrite of previously-received data and to prevent overrunning the buffer. – Martin James Jul 30 '17 at 08:46
  • Also, your question 'the code I've implemented is not working, is giving me a segmentation fault' ....... where? You don't say which line is generating the fault, or even whether it's the server or client, (or both), that is failing:( – Martin James Jul 30 '17 at 08:48

0 Answers0