Socket Programming: Client printing garbage string

Question

I am new to Network Programming and the first program we were supposed to do in our lab was a program where two systems, client and the server send messages to each other. My program has no compiler errors, but whenever a message is sent over the network, it is not being displayed properly on the other end. Instead an unreadable box is being displayed (I think a garbage string is being printed but don't know why).

View the screenshot here

The codes:

client.c

int main()
{
    char server_message[256]="You have reached the server!!\n";
    //create a socket
    int nw_socket;
    nw_socket=socket(AF_INET,SOCK_STREAM,0);

    //specify address for socket

    struct sockaddr_in server_address;
    server_address.sin_family = AF_INET;
    server_address.sin_port = htons(9999);
    server_address.sin_addr.s_addr = INADDR_ANY;

    //establish a connection
    int connection_status = connect(nw_socket, (struct sockaddr *) & server_address, sizeof(server_address));

    //check for errors

    if(connection_status==-1)
    {
        perror("There was a problem initiating the connection.\n");
    }
    else
    {
        printf("The connection was successful.\n");
    }

    int send_val = send(nw_socket,server_message,sizeof(server_message),0);
    if(send_val==-1)
        perror("\nError while sending: ");
    //receive data

    char data[256];
    int recv_val=recv(nw_socket,data,sizeof(data),0);
    if(recv_val==-1)
        perror("\nError while receiving: ");

    printf("The server's response was: %s\n",data );

    //close the socket

    close(nw_socket);

    return 0;
}

server.c

int main()
{
    char server_message[256]="You have reached the server!!\n";

    //create a new socket
    int server_socket=socket(AF_INET,SOCK_STREAM,0);

    struct sockaddr_in server_connection;
    server_connection.sin_family=AF_INET;
    server_connection.sin_port=htons(9999);
    server_connection.sin_addr.s_addr=INADDR_ANY;

    int bind_val=bind(server_socket, (struct sockaddr *) & server_connection, sizeof(server_connection));
    if(bind_val==-1)
        perror("\nError while binding: ");
    listen(server_socket,6);

    int client_socket=accept(server_socket, NULL, NULL);
    if(client_socket==-1)
        perror("\nError while accepting: ");

    int send_val=   send(server_socket,server_message,sizeof(server_message),0);
    if(send_val==-1)
        perror("\nError while sending: ");

    char data[256];
    recv(server_socket,data,sizeof(data),0);
    close(server_socket);

    return 0;
}

How do I fix this? Thanks in advance.

Klas Lindbäck · Accepted Answer · 2018-01-18 11:34:59Z

7

You are using the listening socket when sending a message in the server:

int send_val=   send(server_socket,server_message,sizeof(server_message),0);

You should be using the socket connected to the client:

int send_val = send(client_socket,server_message,sizeof(server_message),0);

answered Jan 18, 2018 at 11:34

Klas Lindbäck

33.4k5 gold badges61 silver badges85 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

JeremyP Over a year ago

Another problem is that recv doesn't put a string in the buffer, just the bytes received. It's fine if the \0 of the string is amongst the bytes received, but it is not guaranteed that that the first recv will return the entire message sent.

Collectives™ on Stack Overflow

Socket Programming: Client printing garbage string

1 Answer 1

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related