CODEWITHSUNDEEP
cmultithreadingsockets
user2269756
user2269756

Reputation: 927

C - Socket Chat Server with thread - Nickname array

I'm doing a chat server using sockets and thread in C, but I have different problem : - I'm not able to send a message to client using his nickname - I've got a problem sending a message and attach the client sender nickname Can you help me on this please ?

How I fix the nickname :

          /* Asks for client nickname */
          if (strcmp(clients_nick[client], "") == 0) {
            write(fd, msg, strlen(msg) * sizeof(char));
            int rc = read(fd, buf, BUFLEN);

            if (rc > 0) {
              /* Deleting the character \n */
              buf[strlen(buf) - 1] = '\0';
              snprintf(clients_nick[client], MAX_NICK_LENGTH - 1, "%s", buf);
            }

          }

How I send the message : void client_write_message ( char * msg, int client_sender, int client_receiver) { char * buffer; buffer = calloc(BUFLEN, sizeof(char));

      snprintf(buffer, BUFLEN, "[%s", clients_nick[client_sender]);
      buffer[strlen(clients_nick[client_sender])] = ']';
      snprintf(buffer, BUFLEN, " %s", msg);

      write(clients[client_receiver], msg, strlen(msg) * sizeof(char));

      buffer[0] = '\0';

      free(buffer);
    }

Upvotes: 0

Views: 757

Answers (1)

hmjd
hmjd

Reputation: 121961

This is incorrect:

buf[strlen(buf) - 1] = '\0';

as read() does not append a null terminator, upon which strlen() depends. The value returned by strlen() is unknown and may result in accessing out of bounds on buf. Remove the null terminator assignment and replace with:

if (rc > 0)
{
    snprintf(clients_nick[client], MAX_NICK_LENGTH - 1, "%.*s", rc, buf);
}

The result of read() is the number of characters read, stored in rc in the posted code, and the format specifier %.*s uses a length and buffer and does not require the buffer to be null terminated.

Upvotes: 2

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