Add UDP echo example

[FObersteiner]

Fix #64

Since I happen to have a Windows 10 notebook on my desk, I did a quick test of the code on Windows. zig run ... does not work, even when I provide a file with libc paths via the --libc flag. What does work is running the program via a build.zig, where you can link libc with exe.linkLibC().

[jinzhongjia]

we can use zig build-exe main.zig -lc, on my notebook, it is windows11, I compile it successfully

[FObersteiner]

we can use zig build-exe main.zig -lc, on my notebook, it is windows11, I compile it successfully

Great, that also works in zig run ....zig -lc. If that works on a "clean" Windows machine, i.e. no Visual Studio build tools etc. installed, we might add that to the cookbook docs, no?

[jinzhongjia]

em...this command is actually explained in the official tutorial

[FObersteiner]

em...this command is actually explained in the official tutorial

I was referring to https://cookbook.ziglang.cc/ - sorry if I have overlooked that.

Concerning the PR: I'm having trouble understanding why the CI fails. It seems to be a problem with chapter 14 / databases; on my machine, this fails with

run-all
└─ run examples-14-03
   └─ zig build-exe examples-14-03 Debug native 1 errors
src/14-03.zig:143:40: error: expected type 'bool', found 'u8'
            if (c.mysql_stmt_bind_param(insert_color_stmt, &color_binds)) {
                ~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Is that related to the UDP example? Did I accidentally use a port that is used by one of the DBs ?

[jinzhongjia]

The mysql_stmt_bind_param function is a directly referenced c function. Maybe it is because the mysql version on your device is different?

[FObersteiner]

The mysql_stmt_bind_param function is a directly referenced c function. Maybe it is because the mysql version on your device is different?

most likely, yes.

IIUC, the problem is that the UDP "server" doesn't get closed automatically after running the example, then CI times out at some point. Didn't check the build.zig... TCP examples are skipped for exactly that reason. Added 04-03 to that list.

[jiacai2050]

Thanks