Question

I keep getting an invalid argument error when I try to connect the client to the server. A couple threads online said this can happen when addrlen is not right, but I tried changing it to a literal value after counting the length and that did not work. I also tried just strlen() with no luck. Anyways, relevant code –

server –

struct sockaddr name;
int main(int agrc, char** argv) {

    int sock, new_sd, adrlen;   //sock is this socket, new_sd is connection socket

    name.sa_family = AF_INET;
    strcpy(name.sa_data, "127.0.0.1");
    adrlen = strlen(name.sa_data) + sizeof(name.sa_family);

    //make socket
    sock = socket(AF_INET, SOCK_STREAM, 0);

    if (sock < 0) {
        printf("\nBind error %m", errno);
        exit(1);
    }  

    //unlink and bind
    unlink("127.0.0.1");
    if(bind (sock, &name, adrlen) < 0)
        printf("\nBind error %m", errno);

    //listen
    if(listen(sock, 5) < 0)
        printf("\nListen error %m", errno);

    //accept
    new_sd = accept(sock, &name, (socklen_t*)&adrlen);
    if( new_sd < 0) {
        printf("\nAccept error %m", errno);
        exit(1);
    }

client –

int main(int agrc, char** argv) {

    int sock, new_sd, adrlen;

    sock = socket(AF_INET, SOCK_STREAM, 0);

    if (sock < 0) {
        printf("\nserver socket failure %m", errno);
        exit(1);
    }

    //stuff for server socket
    name.sa_family = AF_INET;
    strcpy(name.sa_data, "127.0.0.1");
    adrlen = strlen(name.sa_data) + sizeof(name.sa_family);

    cout<<"\nadrlen: "<<adrlen<<"\n";
    if(connect(sock, &name, adrlen) < 0) {
        printf("\nclient connection failure %m", errno);
        exit(1);
    }

I don’t see anything that could be wrong, but I guess I might just be overlooking something or unaware of something. Any help is appreciated.

Answer 1

Well your big problem is completely misunderstanding the sockaddr struct!

Firstly use sockaddr_in.

You would then write code more like the following:

sockaddr_in sai;
sai.sin_family = AF_INET;
sai.sin_port   = htons( 12345 );  /// Or whatever port you wish to use.
inet_aton("127.0.0.1", &sai.sin_addr.s_addr);

Note: htons converts a short value from host to network format. Host could be big or little endian. Network is big endian.