UDP syslog example about rust-syslog

[xenago]

When using 0.0.0.0:0 or :::0 as the local socket address, UDP syslogs seem to be sent successfully.

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Initially I stumbled upon this SO post, it seemed like Ipv4Addr::UNSPECIFIED with the automatic port 0 would help:

It's not obvious, but if you bind the socket to (UNSPECIFIED, 0), then when you connect to a remote address the local address is set to the appropriate interface address. (Port 0 means to auto-allocate a port, just like an unbound socket in C.)

Turns out that 0.0.0.0 is equivalent to UNSPECIFIED in std::net::ToSocketAddrs

An IPv4 address representing an unspecified address: 0.0.0.0

So I tried connecting to a localhost and LAN UDP syslog server with that format, it worked both times:

let syslog_udp_config = fern::Dispatch::new().chain(formatter, "0.0.0.0:0", "127.0.0.1:514").expect("Unable to initialize syslog"));

(...)

let syslog_udp_config = fern::Dispatch::new().chain(formatter, "0.0.0.0:0", "192.168.1.234:514").expect("Unable to initialize syslog"));

It also worked with the IPv6 equivalent, :::0 which is probably an even better choice for future compatibility.

[khumps]

after more testing, I arrived at:

let mut logger = syslog::udp(formatter, "127.0.0.1:1234", "10.0.0.10:514").expect("failed to initialize syslog");
logger.alert("zpe-fixer logging initializing").expect("failed to send syslog message");

However this panics with:

thread 'main' panicked at 'failed to send syslog message: Error(Format, State { next_error: Some(Os { code: 22, kind: InvalidInput, message: "Invalid argument" }), backtrace: InternalBacktrace })', src/main.rs:48:56