TCP connection establishment related questions - c++

Question

I'm reading this code and have several questions about it:
When creating this TCP connection to host and port, it should return a file descriptor on success, and -1 on error. But so far I can only see it returns -1 when connect (s, (struct sockaddr *) &sa, sizeof (sa)) < 0, where did it show it returns a file descriptor on success?
connect (s, (struct sockaddr *) &sa, sizeof (sa)) < 0 What does <0 means here?
Which one is the function of reading the request? If there is none, could you provide me with some good code examples?
int tcpconnect (char *host, int port){
struct hostent *h;
struct sockaddr_in sa;
int s;
/* Get the address of the host at which to finger from the
* hostname. */
h = gethostbyname (host);
if (!h || h->h_length != sizeof (struct in_addr)) {
fprintf (stderr, "%s: no such host\n", host);
return -1;
}
/* Create a TCP socket. */
s = socket (AF_INET, SOCK_STREAM, 0);
bzero (&sa, sizeof (sa));
sa.sin_family = AF_INET;
sa.sin_port = htons (0); /* tells OS to choose a port */
sa.sin_addr.s_addr = htonl (INADDR_ANY); /* tells OS to choose IP addr */
if (bind (s, (struct sockaddr *) &sa, sizeof (sa)) < 0) {
perror ("bind");
close (s);
return -1;
}
sa.sin_port = htons (port);
sa.sin_addr = *(struct in_addr *) h->h_addr;
/* And connect to the server */
if (connect (s, (struct sockaddr *) &sa, sizeof (sa)) < 0) {
perror (host);
close (s);
return -1;
}
return s;
}

Answer 1

When creating this TCP connection to host and port, it should return a file descriptor on success, and -1 on error. But so far I can only see it returns -1 when connect (s, (struct sockaddr *) &sa, sizeof (sa)) < 0, where did it show it returns a file descriptor on success?
s = socket(...) creates the actual file descriptor, and then return s; returns that file descriptor to the caller of tcpconnect() if nothing goes wrong. If anything does goes wrong, the code is releasing the file descriptor with close(s) and then returning -1 to the caller.
connect (s, (struct sockaddr *) &sa, sizeof (sa)) < 0 What does <0 means here?
connect() returns 0 on success, and negative on failure. The code is simply checking if connect() fails. Same as it is doing with bind() (and should be doing with socket()).
Which one is the function of reading the request?
There is nothing in the code shown that is reading a request. That happens outside of this code, after tcpconnect() returns a valid file descriptor to the caller.