CODEWITHSUNDEEP
c++unixtcp
Richard John Catalano
Richard John Catalano

Reputation: 449

TCP Server C++/Unix commandline

I am programming a TCP server in C++, and this is my first time doing it. The problem I am running into seems to be toward the bottom with the strcmp function. I have established the server, then I fork my processes and run the request from the child process. This works fine. For some reason, when I input GET /stuff/ it won't accept GET and automatically prints the error message "Invalid first argument". I have no space problems, so what's the deal? Any ideas are very much appreciated. 

void processClientRequest(int connSock, struct sockaddr_in echoclient) //char *argv[] )
{
    char buffer[256];
    unsigned int recieved, count = 0;

    if ((recieved = read(connSock, buffer, 256)) < 0) { //read a message from the client
            perror ("Failed to recieve message");
            exit (EXIT_FAILURE);
    }

    buffer[recieved] = '\0'; //ensure string is terminated
    chomp(buffer); //remove trailing \r and \n

    if (write(connSock, buffer, recieved) != recieved) {
            perror ("Mismatch in number of echo'd bytes");
            exit(EXIT_FAILURE);
    }

    // prepare argv array of strings
    char *argv[] = { (char*)0, (char*)0, (char*)0, (char*)0, (char*)0, (char*)0, (char*)0 };

    // parse command into words
    for (char *p = strtok(buffer, " "); p; p = strtok(NULL, " "))
            {   argv[count] = p;
                    count++;
            }

    cout << "THIS IS ARGV[0]" << argv[0] << endl; //debugging, for some reason will not print

    if (strcmp (argv[0], "GET") == 0)
            GET(connSock, argv[1]);

    else if (strcmp(argv[0], "INFO") == 0)
            INFO();

    else
    {
            perror("Invalid first argument!");
            exit(EXIT_FAILURE);
    }

    // run command and its arguments via execvp
    /*      if (execvp(argv[0], argv) < 0) {
            perror("exec in child after fork");
            exit(EXIT_FAILURE);
            }*/

    cerr << "Client(" << inet_ntoa(echoclient.sin_addr) << ") sent: " << buffer << endl;

}

Upvotes: 0

Views: 296

Answers (1)

David Schwartz
David Schwartz

Reputation: 182753

The read function doesn't receive messages, it receives bytes. If you want to receive messages, and you do, you have to write a function to receive them. That requires following the rules of the HTTP protocol to keep receiving bytes until you have the entire messsage, whether that's a line, the entire header, or whatever.

This has probably been said thousands of times, "TCP is a reliable byte-stream protocol that does not preserve application message boundaries." Until you 100% understand what TCP is, don't write code that uses TCP. It will never work correctly.

Upvotes: 1

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