Code sippet needs explaining

Hello,

I have just started socket programming.

I am having trouble understanding this line of code.

Code:

---

bind(int socket, struct sockaddr *address, int address_length);

---

I am using it like this:

Code:

---

bind(s, (struct sockaddr *)&sin, sizeof(sin));

---

I can understand the 1st and 3rd parameters, but can't understand the second.

Code:

---

(struct sockaddr *) &sin

---

My idea is that it is passing the &sin by reference and casting it to a pointer to a struct of sockaddr.

Correct me if I am wrong,

Any examples would be good for me.

Many thanks for your help,

Steve

You are correct. This is because "sockaddr" is a generic form, and your "sin" is (I guess) of type "sockaddr_in", so the compiler would complain if you didn't have the cast.

--
Mats

You are correct that it's casting it to a pointer to struct sockaddr, but C does not have "pass by reference". You are passing a pointer to sin.

Hello,

Thanks for your response.

Quote:

---

but C does not have "pass by reference"

---

Does this mean that you can use references in your code but you cannot pass them by reference in your functions.

Many thanks.

Steve

Quote:

---

Does this mean that you can use references in your code but you cannot pass them by reference in your functions.

---

It depends on what is meant by "reference". C does not have C++ style references. C can simulate pass by reference using pointers.

I think it helps to read '&' as "address of" or "pointer to" in C.
Therefore

&sin would be read "the address of sin"

and

(struct sockaddr *)&sin would be read "the address of sin cast as a pointer to a sockaddr structure"

I agree. I find it better to separate the two terms. References are C++ only.
Another thing one might note is that it requires a cast since C doesn't support classes and polymorphism either. In C++, it would be easy to pass it without a cast. But this is C :p