C client/server program: server sends answer multiple times when it shouldn't

Question

I have the following scenario in C: a simple client program sends HTTP-like requests to a server, which is then supposed to return the input of the specified file. So far, there are only three methods the server should support: GET, HEAD and a default answer for bad requests.

Here's part of the server program:

for(;;){
    struct sockaddr_in clientAddr;
    int clientAddrLen = sizeof(clientAddr);
    int clientSocket;
    
    clientSocket = accept(serverSocket, (struct sockaddr*)&clientAddr, &clientAddrLen);
    
    char buf[BUFSIZE];
    int bytesRecv;
    
    
    bytesRecv = recv(clientSocket, (char*)&buf, BUFSIZE, 0);
    while(bytesRecv > 0){
        char *method;
        method = strtok(buf, " ");
        printf("method %s\n", method);
        if(strncmp(method, head, 4) == 0){
            /*HEAD*/
            char answer[] = "method: HEAD\0";
            send(clientSocket, answer, sizeof(answer) + 1, 0);
        }else{
            if (strncmp(method, get, 3) == 0){
                /*GET*/
                char answer[] = "method: GET\0";
                send(clientSocket, answer, sizeof(answer) + 1, 0);
            }else{
            
                /*bad request*/
                char answer[] = "HTTP/1.1 400 Bad Request\0";
                send(clientSocket, answer, sizeof(answer) + 1, 0);
            }   
        }
        
        /*Read*/
        bytesRecv = recv(clientSocket, (char*)&buf, BUFSIZE, 0);
    }

And this is the part of the client program, that asks to enter a request on the command line and then sends the respective input:

char* server_reply[1024];
char* msg[100];

/*send requests*/
for(;;){
    printf("Request:\n");
    scanf("%s", &msg);
    
    if(strcmp(msg, "quit") == 0){
        break;
    }

    send(clientSocket, msg, sizeof(msg), 0);

    if(recv(clientSocket, server_reply, sizeof(server_reply), 0) < 0){
        printf("Failure in recv.");
    }else{
        printf("Server: %s\n", server_reply);
    }
}

Now, the problem is the following: When I enter for example "GET HEAD asd" on the client side, I get three answers from the server, namely

method: GET

method: HEAD

HTTP/1.1 400 Bad Request

when it actually should only be "method: GET". I really don't understand this beaviour ... Thanks for your help!

We are working together at this project. But the purpose of my question was another, we encountered this problem after solving the one I've posted. — Valentino Ru, Apr 01 '13 at 18:02

score 2 · Accepted Answer · answered Apr 01 '13 at 18:01

2

scanf("%s", &msg);

Reads strings Not a whole line. Which means when you enter GET HEAD asd your loop runs three times.

First it reads GET sends it
and then HEAD sends it
and then asd

answered Apr 01 '13 at 18:01

Ok, is there an alternative to scanf? – kafman Apr 01 '13 at 18:03
It depends. How do you want to interpret `GET HEAD asd`? as `GET` and then `HEAD asd`? – Apr 01 '13 at 18:05
I'd like to read the whole line. The server then takes care if GET or HEAD precedes the statement. – kafman Apr 01 '13 at 18:13
Then check this http://stackoverflow.com/questions/314401/how-to-read-a-line-from-the-console-in-c – Apr 01 '13 at 18:13
then use `getLine` from there instead of `scanf` – Apr 01 '13 at 18:15

C client/server program: server sends answer multiple times when it shouldn't

1 Answers1