LinuxQuestions.org - read(newsockfd, buffer ,to read) sometimes getting struck

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read(newsockfd, buffer ,to read) sometimes getting struck

Hello Everyone,

I have written socket programming in c++.
some times my read will get strucked.

Code:





void handlesocket(int newsockfd)

{

        char *buffer, *temp, *temp2;

        int n,i;

        int readNow, toRead;

        if (newsockfd < 0)

                error("ERROR on accept");



        buffer = new char[960000];

        temp = new char[16];

        temp[0] = '\0';

        temp2 = new char[1];

        temp2[0] = '\0';

        i = 0;

        do

        {

                n = read(newsockfd,temp2, 1);

                if(temp2[0]=='@') break;

                temp[i++] = temp2[0];

                temp[i] = '\0';

        }

        while(n > 0);



        n = 0;

        do

        {

                buffer[0] = '\0';

                toRead = atoi(temp) - n;

          printf("ready to read\n ToRead=%d\n",toRead);

         //Sometime strucking at this next line

            readNow = read(newsockfd,buffer,toRead);

                printf("ReadNow is %d\n",readNow);

                if(readNow < 0) break;

                n += readNow;

                printf("ISAC %d --- %d --- %d\n",atoi(temp),n,readNow);

                buffer[readNow] = '\0';

                writeintofile(buffer);

        }

        while(n < atoi(temp));

  close(newsockfd);

        free(buffer);

        free(temp);

        free(temp2);

}

Please help me out...

check your lenght ... and read return values

1/ You dont check if the lenght is correct (you're expecting to read more than what you'll have to).
2/ You have to test the return value of read system call (take a look into the manpage).

By the way, dont you have to allocate memory for your temporary variables (except for your read buffer, it can't fit in stack in some systems). I think that you should use something like this :

Code:

void handlesocket(int newsockfd)

{

#define MAX 960000

    int i, n, lenght, done;

    char temp2;

    char * buffer;

    char temp[16];



    if (newsockfd < 0) {

        fprintf(stderr, "Failed to read lenght from socket : %m\n");

        return;

    }



    i = 0;

    while (1) {

        n = read(newsockfd, &temp2, 1);

        if (n < 0) {

            if (errno != EAGAIN && errno != EWOULDBLOCK) {

                fprintf(stderr, "Failed to read lenght from socket : %m\n");

                return;

            }



            n = 0;

        }



        if (temp2 == '@')

            break;



        if (i >= sizeof temp) {

            fprintf(stderr, "Toooo long lenght received (max = %d, %d received so far)\n", sizeof temp, i);

            return;

        }



        temp[i++] = temp2;

        temp[i] = '\0';

    }



    lenght = atoi(temp);

    if (lenght <= 0 || lenght >= MAX) {

        fprintf(stderr, "Invalid lenght received : %s\n", temp);

        return;

    }



    buffer = new char [lenght + 1];

    if (buffer == NULL) {

        fprintf(stderr, "Cannot create buffer of %db\n", lenght + 1);

        return;

    }



    printf("Reading %d bytes\n", lenght);



    do {



        n = read(newsockfd, buffer + done, lenght - done);

        if (n < 0) {

            if (errno != EAGAIN && errno != EWOULDBLOCK) {

                fprintf(stderr, "Failed to read data from socket : %m\n");

                return;

            }

            n = 0;

        }



        done += n;



    } while (done < lenght);



    buffer[lenght] = 0;

    writeintofile(buffer);

    close(newsockfd);

    delete buffer;

}