What is SOCK_DGRAM and SOCK_STREAM?
I just came across this strange thing I got to see application is that by default they use SOCK_STREAM function. Why is it so? Is this SOCK_STREAM just creating multiple streams? Or is it the standard SOCK_STREAM function available for creating TCP stream(s)?
I thought tsunami is based on UDP, but still having some features like that of TCP, e.g. TCP fairness, friendlyness, etc.
Could somebody please shed some light on this issue? I am totally confused over this.
Answer
TCP almost always uses SOCK_STREAM and UDP uses SOCK_DGRAM.
TCP (SOCK_STREAM) is a connection-based protocol. The connection is established and the two parties have a conversation until the connection is terminated by one of the parties or by a network error.
UDP (SOCK_DGRAM) is a datagram-based protocol. You send one datagram and get one reply and then the connection terminates.
If you send multiple packets, TCP promises to deliver them in order. UDP does not, so the receiver needs to check them, if the order matters.
If a TCP packet is lost, the sender can tell. Not so for UDP.
UDP datagrams are limited in size, from memory I think it is 512 bytes. TCP can send much bigger lumps than that.
TCP is a bit more robust and makes more checks. UDP is a shade lighter weight (less computer and network stress).
Choose the protocol appropriate for how you want to interact with the other computer.