Issue with popen() fread()

Hi everyone. I just started C this weekend so sorry if I am extremely confused with everything.

I am very new to C so sorry if I am really confused.

I am trying to have a server process fork() another process to run a C program through popen(). But as soon as I attempt to read the bytes, I get an error from my accept() in my main server process. Here is where I am getting the error.

Can someone please help.

Code:

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                    pipe_pointer = popen(cgi_command, "r");
                   
                    if(pipe_pointer != NULL) {
                        while(!feof(pipe_pointer)) {
                            bytes_read = fread(buf, 1, sizeof(buf), pipe_pointer);
                           
                            send(clientSock, buf, bytes_read, 0);
                       
                        }
                    }
                   
                   
                    pclose(pipe_pointer);

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Here is the entire code

Code:

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    /**
    * This method processes the first line of the HTTP request and stores it in the variable that the pointer
    * buffer points to. In this case that variable is the request variable in the request_handler method. Returns 0 if nothing was received.
    **/
    int process_request(int clientSock, char *buffer) {
        #define EOL "\r\n"
        #define EOL_SIZE 2
       
        char *bufferPointer = buffer;
        int eol_matched = 0;
       
        while(recv(clientSock, bufferPointer, 1, 0) != 0) {
            if(*bufferPointer == EOL[eol_matched]) {
                ++eol_matched;
               
                if(eol_matched == EOL_SIZE) {
                    *(bufferPointer+1-EOL_SIZE) = '\0';
                    return(strlen(buffer));
                }
            }
            else {
                eol_matched = 0;
            }
            bufferPointer++;
        }
        return(0);
    }
   
    int validate_get_request(char *buffer) {
        char get_string[5] = "GET /";
        if(strncasecmp(buffer, get_string, 5) != 0) {
            return(-1);
        }
        else {
            return(1);
        }
    }
   
    /**
    *This method takes a valid request and a pointer to a empty path variable, then fills out the path variable with the path of the requested file. Also it stores the requested filename in the filename variable
    **/
    void get_path(char *request, char *path, char *filename) {
        char buf[1024];
        int i = 0;
        char *pointer = request;
        pointer += 4;
        while(!ISspace(pointer[i]) && pointer[i] != '\0') {
            filename[i] = pointer[i];
            i++;
        }
        filename[i] = '\0';
       
   
        if(strcmp(filename, "/") == 0) {
            strcpy(filename, "/index.html");
        }
       
        if(strstr(filename, ".cgi") != NULL) {
            strcpy(path, CGIROOT);
        }
        else {
            strcpy(path, DOCROOT);
        }
        strcat(path, filename);
    }
   
   
    void send_ok_header(int clientSock, char *mime) {
        char buf[1024];
        //Create OK Header, then add the file
       
        strcpy(buf, "HTTP/1.0 200 OK\r\n");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, SERVER);
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "Content-Type: ");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, mime);
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "\r\n\r\n");
        send(clientSock, buf, strlen(buf), 0);
    }
   
    void send_not_found(int clientSock, char *mime) {
        char buf[1024];
        //Create not found Header, then add the file
        strcpy(buf, "HTTP/1.0 404 NOT FOUND\r\n");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, SERVER);
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "Content-Type: ");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, mime);
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "\r\n\r\n");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "404 Sorry this webpage cannot be found\n");
        send(clientSock, buf, strlen(buf), 0);
    }
   
    void send_unsupported(int clientSock, char *mime) {
        char buf[1024];
        //Create not found Header, then add the file
        strcpy(buf, "HTTP/1.0 415 UNSUPPORTED MEDIA TYPE\r\n");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, SERVER);
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "Content-Type: ");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, mime);
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "\r\n\r\n");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "415 Sorry this media type is not supported!!!\n");
        send(clientSock, buf, strlen(buf), 0);
    }
   
    void send_unimplemented(int clientSock, char *mime) {
        char buf[1024];
        //Create not found Header, then add the file
        strcpy(buf, "HTTP/1.0 501 UNIMPLEMENTED\r\n");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, SERVER);
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "Content-Type: ");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, mime);
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "\r\n\r\n");
        send(clientSock, buf, strlen(buf), 0);
        strcpy(buf, "501 Sorry this server only implements valid GET request\n");
        send(clientSock, buf, strlen(buf), 0);
    }
   
   
   
    /**
    This method takes the filename and fills the variable mime with its appropriate MIME type. Returns -1 if there is an unrecognized filename
    **/
    int get_mime_type(char *filename, char *mime, int *is_cgi) {
        //WHY DOES THIS START WITH SOME WEIRD INITIAL VALUE ON THE 2ND TIME A REQUEST IS MADE?????
        char extension[50] = "";
        int return_val = -1;
        char *pointer;
        int filename_len = sizeof(filename);
        int i = 0;
       
        pointer = strstr(filename, ".");
        if(pointer != NULL) {
            while(pointer[i] != '\0') {
                extension[i] = pointer[i];
                i++;
            }
        }
   
       
        if(strcasecmp(extension, ".html") == 0 || strcasecmp(extension, ".htm") == 0) {
            strcpy(mime, "text/html");
            return_val = 1;
        }
       
        else if(strcasecmp(extension, ".jpeg") == 0 || strcasecmp(extension, ".jpg") == 0) {
            strcpy(mime, "image/jpeg");
            return_val = 1;
        }
       
        else if(strcasecmp(extension, ".gif") == 0) {
            strcpy(mime, "image/gif");
            return_val = 1;
        }
       
        else if(strcasecmp(extension, ".txt") == 0) {
            strcpy(mime, "text/plain");
            return_val = 1;
        }
       
        //set the cgi variable to 1
        else if(strcasecmp(extension, ".cgi") == 0) {
            strcpy(mime, "text/html");
            *is_cgi = 1;
            return_val = 1;
        }
       
       
       
        return(return_val);
    }
   
   
   
    /**
    * This is the function that the handler thread executes to handle each request
    */
    void request_handler(int clientSock) {
        FILE *pipe_pointer = NULL;
        int i = 0;
        int is_cgi = 0;
        char buf[1024], path[1024], request[1024], mime[20], filename[50], *query_string[50] = {NULL}, *query_pointer, cgi_command[1024], cgibuf[1024];
        long bytes_read;
       
        //Send the actual html file with header
        FILE *requestedfile = NULL;
       
        //Take a request and fill it in the request variable
        if(process_request(clientSock, request) != 0) {
            //If it is a get request
            if(validate_get_request(request) != -1) {
               
               
                query_pointer = strtok(request, " ?=&");
                strcpy(request, query_pointer);
                while(query_pointer != NULL) {
                    query_string[i] = malloc(strlen(query_pointer) + 1);
                    strcpy(query_string[i], query_pointer);
                    query_pointer = strtok(NULL, " ?=&");
                    i++;
                }
                query_string[i] = NULL;
               
               
                get_path(request, path, filename);
               
                access(path, R_OK);
               
                //if the file extension is unsupported throw a 415 code
                if(get_mime_type(filename, mime, &is_cgi) != 1) {
                    send_unsupported(clientSock, mime);
                }
                else if(errno == ENOENT) { //filetype is recognized, but file cannot be found
                    send_not_found(clientSock, mime);
                }
                else if(errno == EACCES) { //filetype and file found, but no read access to the file
                    //fix this to a 403 error
                    perror("no access");
                }
                else { //PUT THE CGI code somewhere in this else statement
                   
                    if(is_cgi == 1) {
                        i = 1;
                        //Create command to open cgi script
                        strcpy(cgi_command, "(cd ");
                        strcat(cgi_command, CGIROOT);
                        strcat(cgi_command, "; .");
                        strcat(cgi_command, filename);
                        strcat(cgi_command, " ");
                       
                       
                        while(query_string[2*i + 1] != NULL) {
                            strcat(cgi_command, query_string[2*i + 1]);
                            i++;
                        }
                        strcat(cgi_command, ")");
                       
                        free(*query_string);
                       
                       
                       
                       
                       
                        pipe_pointer = popen(cgi_command, "r");
                       
                        if(pipe_pointer != NULL) {
                            while(!feof(pipe_pointer)) {
                           
                                bytes_read = fread(cgibuf, 1, sizeof(cgibuf), pipe_pointer);
                               
                                send(clientSock, cgibuf, bytes_read, 0);
                           
                            }
                        }
                       
                       
                        pclose(pipe_pointer);
                    }
                    else {
                        //Open the file and start to send it
                        requestedfile = fopen(path, "rb");
   
                        //Send header
                        send_ok_header(clientSock, mime);
           
                        //Read the file by 1024 byte increments and send it
                        while(!feof(requestedfile)) {
                            bytes_read = fread(buf, 1, sizeof(buf), requestedfile);
                            send(clientSock, buf, bytes_read, 0);
                           
                        }
                    }
                }
           
            }
            else { //not a get request
               
                send_unimplemented(clientSock, mime);
   
            }
        }
        //Close the client socket when the request is fulfilled
        //thread will die after this
        close(clientSock);
    }
   
    int main(int argc, const char * argv[])
    {
        int server_sock_desc;
        struct sockaddr_in name;
       
        int client_sock_desc;
        struct sockaddr_in client_name;
        socklen_t addr_size;
       
        pthread_t handler_thread;
       
        //connection setup
        server_sock_desc = socket(PF_INET, SOCK_STREAM, 0);
        if(server_sock_desc != -1) {
            memset(&name, 0, sizeof(name));
            name.sin_family = AF_INET;
            name.sin_port = htons(PORTNUMBER);
            name.sin_addr.s_addr = htonl(INADDR_ANY);
            int bind_result = bind(server_sock_desc, (struct sockaddr *) &name, sizeof(name));
            if(bind_result == 0) {
                if(listen(server_sock_desc, BACKLOG) < 0) {
                    perror("listen failed");
                }
               
                addr_size = sizeof(client_name);
               
                //Server Loop will continue to run listening for clients connecting to the server
                while(1) {
                   
                    //new client attempting to connect to the server
                    client_sock_desc = accept(server_sock_desc, (struct sockaddr *) &client_name, &addr_size);
                    if(client_sock_desc == -1) {
                        perror("accept failed");
                    }
           
                    //connection starts here
                   
                    //create a thread for the new clients request to be handled
                    if(pthread_create(&handler_thread, NULL, request_handler, client_sock_desc) != 0) {
                        perror("pthread_create failed");
                    }
                }
            }
            else {
                perror("bind failed");
            }
        }
        else {
            perror("socket failed");
        }
   
    }

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After fread() is executed program execution immediately jumps to this loop and gets stuck on the second line

Code:

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    while(recv(clientSock, bufferPointer, 1, 0) != 0) {
            if(*bufferPointer == EOL[eol_matched]) {
                ++eol_matched;
   
                if(eol_matched == EOL_SIZE) {
                    *(bufferPointer+1-EOL_SIZE) = '\0';
                    return(strlen(buffer));
                }
            }
            else {
                eol_matched = 0;
            }
            bufferPointer++;
        }

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I really hope someone can help me out. I am extremely lost

> strcpy(buf, "HTTP/1.0 200 OK\r\n");
> send(clientSock, buf, strlen(buf), 0);
You should create a new utility function, say

Code:

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void sendString ( int clientSock, const char *buf ) {
  send(clientSock, buf, strlen(buf), 0);
}

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Then you can write

Code:

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    sendString(clientSock, "HTTP/1.0 200 OK\r\n");
    sendString(clientSock, buf);
    sendString(clientSock, SERVER);
    sendString(clientSock, "Content-Type: ");
    sendString(clientSock, mime);
    sendString(clientSock, "\r\n\r\n");

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-
> int filename_len = sizeof(filename);
You probably meant strlen here, since filename is a pointer.
It's a good job you don't actually use it.

Code:

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>        while(pointer[i] != '\0') {
            extension[i] = pointer[i];
            i++;
        }

---

You just implemented strcpy again.

> *is_cgi = 1;
Ideally, you should have
*is_cgi = 0;
at the start of the function, just to make it plain that this is the single special case.


> while(query_pointer != NULL)
Add
while(query_pointer != NULL && i < 50 )
to make sure you don't overflow the array.


> while(query_string[2*i + 1] != NULL)
I would suggest a proper for loop, based on the known number of parameters.
If someone feeds in a badly formatted request which results in an odd number of tokens, then you're borked.

> free(*query_string);
This is plain wrong.
You have
query_string[i] = malloc(....
That means you need
free(query_string[i]);
for each element you allocated.

> while(!feof(requestedfile))
SourceForge.net: Feof - cpwiki
Try instead

Code:

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while ( (bytes_read = fread(buf, 1, sizeof(buf), requestedfile)) != 0 )
    send(clientSock, buf, bytes_read, 0);

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Quote:

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Hi everyone. I just started C this weekend so sorry if I am extremely confused with everything.

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o_0

Maybe you should...I don't know...start with something a little more basic than trying to write a web server???