[wutwutwat]

Unix sockets can use tcp, udp, or be a raw stream

https://en.wikipedia.org/wiki/Unix_domain_socket#:~:text=The....

Puma creates a `UnixServer` which is a ruby stdlib class, using the defaults, which is extending `UnixSocket` which is also using the defaults

https://github.com/puma/puma/blob/fba741b91780224a1db1c45664...

Those defaults are creating a socket of type `SOCK_STREAM`, which is a tcp socket

> SOCK_STREAM will create a stream socket. A stream socket provides a reliable, bidirectional, and connection-oriented communication channel between two processes. Data are carried using the Transmission Control Protocol (TCP).

https://github.com/ruby/ruby/blob/5124f9ac7513eb590c37717337...

You still have the tcp overhead when using a local unix socket with puma, but you do not have any network overhead.

[FaceValuable]

Hey! I know it’s muddled but that’s not quite correct. SOCK_STREAM is more general than TCP; SOCK_STREAM just means the socket is a byte stream. You would need to add IPPROTO_TCP on top of that to pull in the TCP stack.

UDS using SOCK_STREAM does not do that; ie, it is not using IPPROTO_TCP.

[shawn_w]

Unix domain stream sockets do not use tcp. Nor do unix datagram sockets use udp. They're much simpler.

[wutwutwat]

>The type parameter should be one of two common socket types: stream or datagram.[10] A third socket type is available for experimental design: raw.

> SOCK_STREAM will create a stream socket. A stream socket provides a reliable, bidirectional, and connection-oriented communication channel between two processes. Data are carried using the Transmission Control Protocol (TCP).

> SOCK_DGRAM will create a datagram socket.[b] A Datagram socket does not guarantee reliability and is connectionless. As a result, the transmission is faster. Data are carried using the User Datagram Protocol (UDP).

> SOCK_RAW will create an Internet Protocol (IP) datagram socket. A Raw socket skips the TCP/UDP transport layer and sends the packets directly to the network layer.

I don't claim to be an expert, I just have a certain confidence that I'm able to comprehend words I read. It seems you can have 3 types of sockets, raw, udp, or tcp.

https://en.wikipedia.org/wiki/Unix_domain_socket

[FaceValuable]

Interesting! The Wikipedia article is quite wrong here. SOCK_STREAM certainly doesn’t imply TCP in all cases. I see the source is the Linux Programming Interface book; quite likely someone’s interpretation of that chapter was just wrong when they wrote this article. It is a subtle topic.

[shawn_w]

Not the first time a Wikipedia article has been wrong. That one seems to be talking about IP sockets and local ones at the same time instead of focusing on local ones. Could definitely stand to be rewritten.

[rcxdude]

Yeah, someone's gotten confused. SOCK_DGRAM and SOCK_STREAM imply TCP and UDP when using AF_INET sockets, but not when using AF_UNIX sockets, though unix domain sockets do often somewhat do an impression of a TCP socket (e.g. they will report a connection state in the same way as TCP). Reads and writes to unix domain sockets essentially amount to the kernel copying memory between different processes (interestingly, linux will also do the same for local TCP/UDP connections as well, as an optimisation. So the data never actually gets formatted into separate packets). This also accounts for some of the things you can do with unix sockets you can't do with a network protocol, like pass permissions and file descriptors across them.