I am (trying) to write a bit of a webserver and I have made progress but although it is basicaly working I am getting a load of wierd problems.
When I open a connection to the server in telnet and type "testp" and then "test" it will print "testp" both times, but this does not happen reliably, it only seems to happen when going from a >4 character word to a 4 character word, it doesn't happen with 1 2 3 letter words etc, very odd!
The "free(html_command);" with the BOB printf's around it is sometimes returning a message like this "free(): invalid pointer 0x804b030!" which I don't understand. Its not constant, when I connect to the program via telnet and type things it produces the free error sometimes but not most of the time and I see no pattern in it. I also can't see the problem in the code as that is the only place where that variable is freed so surely if its not NULL there shouldn't be a problem, and I check that its not NULL!
When I start spamming the thing by typing alot (which I guess is like recieving lots of tiny messages) it seg faults. Unfortunately gdb doesn't seem to say anything handy:
"Program received signal SIGSEGV, Segmentation fault.
0x4008f346 in mallopt () from /lib/tls/libc.so.6"
When I point my web-browser at the program it recievs the first line fine but then replaces the other lines with the Ø symbol.
I suspect the problem is with the code that copys the recieved stuff between the buffer, the sockets buffer and the html_command but I am not really sure so I will paste the whole lot incase I miss off somthing important.
ThanksCode:#include <stdio.h> #include <sys/socket.h> #include <netinet/in.h> #include <stdbool.h> #define PORT 1337 #define BACKLOG 10 /* Function delarations */ int main(int argc, char *argv[]); int init(); void get_input(); /* Global variables */ int sin_size; int fdmax; /* The largest file descriptor number being used */ struct sockaddr_in my_address; /* Server address */ struct sockaddr_in their_address; /* Client address */ int listener_fd, new_fd; /* Listening socket and newly made sockets */ fd_set master_fd_set; /* Master file descriptor list */ fd_set read_fd_set; /* Temp list for select() */ struct Ssocket { int fd; /* File descriptor */ char *buffer; int buffer_length; struct Ssocket *next; struct Ssocket *prev; }; struct Ssocket *first_socket; char *html_command; int html_command_size; int main(int argc, char *argv[]) { bool running = false; int i; /* Initialize stuff */ if (init() == -1) { printf("Failed to init.\n"); exit(1); } else running = true; /* Listen for connections */ if (listen(listener_fd, BACKLOG) == -1) { printf("Problem listening for connections\n"); exit(1); } FD_SET(listener_fd, &master_fd_set); /* Add the new socket to the set */ fdmax = listener_fd; /* set the biggest fd as the current one */ while (running == true) get_input(); /* Tidy up before we go */ close(new_fd); for (i = 0; i <= fdmax; i++) close(i); FD_ZERO(&master_fd_set); FD_ZERO(&read_fd_set); close(listener_fd); } int init() { /* Start the socket file descriptor */ if ((listener_fd = socket(AF_INET, SOCK_STREAM, 0)) == -1) { printf("Couldn't open the socket!\n"); return(-1); } /* Assign the stuff */ my_address.sin_family = AF_INET; my_address.sin_port = htons(PORT); /* Set the port to the one defined */ my_address.sin_addr.s_addr = htonl(INADDR_ANY); /* Set the sockets IP to local */ memset(&(my_address.sin_zero), '\0', 8); /* Zero the rest */ /* Bind the socket to the port */ if (bind(listener_fd, (struct sockaddr *)&my_address, sizeof(struct sockaddr)) == -1) { printf("Couldn't bind the socket's port!\n"); return(-1); } /* Figure this out to save complication later */ sin_size = sizeof(struct sockaddr_in); /* Zero the socket sets */ FD_ZERO(&master_fd_set); /* Clear the */ FD_ZERO(&read_fd_set); /* sets */ /* Reset the html command */ html_command = NULL; html_command_size = 0; return 0; } void get_input() { char buffer[100]; int i, j, k, addrlen, nbytes; struct Ssocket *current_socket; struct Ssocket *new_socket; struct Ssocket *socket; read_fd_set = master_fd_set; /* Copy it */ if (select(fdmax + 1, &read_fd_set, NULL, NULL, NULL) == -1) { printf("Problem with the socket set select watsit\n"); exit(1); } for (i = 0; i <= fdmax; i++) if (FD_ISSET(i, &read_fd_set)) /* loop through each socket */ if (i == listener_fd) /* Its a new connection */ { addrlen = sizeof(their_address); if ((new_fd = accept(listener_fd, (struct sockaddr *)&their_address, &addrlen)) == -1) { printf("Problem accepting the connection"); exit(1); } else { FD_SET(new_fd, &master_fd_set); if (new_fd > fdmax) fdmax = new_fd; /* Keep the max the max */ /* Add socket's structure to the linked list */ new_socket = malloc(sizeof(struct Ssocket)); new_socket->fd = new_fd; new_socket->buffer = NULL; new_socket->buffer_length = 0; new_socket->next = first_socket; if (first_socket != NULL) first_socket->prev = new_socket; first_socket = new_socket; printf("New connecton (%d) from %s\n", new_fd, inet_ntoa(their_address.sin_addr)); } } else /* Its data from an already connected client */ { nbytes = recv(i, buffer, sizeof(buffer), 0); /* Get the pointer of the socket structure */ current_socket = first_socket; while (current_socket != NULL) { if (current_socket->fd == i) { socket = current_socket; break; } current_socket = current_socket->next; } /* Reset the html command size */ html_command_size = 0; switch (nbytes) { case 0: printf("Socket quit (%d)\n", i); close(i); FD_CLR(i, &master_fd_set); /* Clean up the socket structure */ if (socket->next != NULL) socket->next->prev = socket->prev; if (socket->prev != NULL) socket->prev->next = socket->next; if (socket == first_socket) first_socket = first_socket->next; if (socket->buffer != NULL) free(socket->buffer); free(socket); break; case -1: /* Could maybe just ignore instead of kicking */ printf("Error recieving so kicking client\n"); close(i); FD_CLR(i, &master_fd_set); /* Clean up the socket structure */ if (socket->next != NULL) socket->next->prev = socket->prev; if (socket->prev != NULL) socket->prev->next = socket->next; if (socket == first_socket) first_socket = first_socket->next; if (socket->buffer != NULL) free(socket->buffer); free(socket); break; default: /* Allocate space in the sockets buffer */ if (socket->buffer_length <= 0) socket->buffer = malloc(nbytes + 1); else socket->buffer = realloc(socket->buffer, socket->buffer_length + nbytes + 1); /* Put the recieved guff in the sockets buffer */ for (j = socket->buffer_length; j < socket->buffer_length + nbytes; j++) socket->buffer[j] = buffer[j - socket->buffer_length]; socket->buffer[j + 1] = '\0'; socket->buffer_length += nbytes; /* printf("%s\n",socket->buffer); */ for (j = 0; j < socket->buffer_length; j++) { if (socket->buffer[j] == '\n' || socket->buffer[j] == '\r') { /* Get the html command buffer the right size */ html_command_size = j; printf("BOB\n"); if (html_command != NULL) free(html_command); printf("BOBB\n"); html_command = malloc(j + 1); /* Copy the stuff into the html command bufer */ for (k = 0; k < j; k++) html_command[k] = socket->buffer[k]; html_command[k + 1] = '\0'; /* Remove the dealt with stuff from the sockets buffer */ socket->buffer_length -= (j + 2); /* + 2 to get rid of the '\n' and stuff */ if (socket->buffer_length <= 0) { free(socket->buffer); socket->buffer = NULL; } else { for (k = 0; k < socket->buffer_length; k++) socket->buffer[k] = socket->buffer[k+j]; socket->buffer[k+1] = '\0'; socket->buffer = realloc(socket->buffer, socket->buffer_length); } printf(".%s.\n", html_command); break; } } break; } } }
