Remove an incorrect TODO
Fix blank nicks appearing on everyone else's screen
Defer command recognition until server confirms
Make  work even without a nick
Freshly bake syntax errors thereby preventing random segfaults
Fix options with = sign doesn't take next argument when unspecified
Fix: `getaddrinfo` returns positive on error
Implement Ambiguous options
Make `=` optional
Add address family choice options
Fix default hostname gets corrupted for `--port=PORT`
Parse --long-options=
Begin parsing command line options
Zero-initialize client's nick
Include header defining `struct sockaddr_in`

Quick test on FreeBSD 13.0-STABLE revealed that `main.c` will not
compile and missing definition for `struct sockaddr_in` and `struct

ariel $ uname -sr

ariel $ gmake
cc -Wall -Wextra -pedantic -g -O0 -std=c99 -D_POSIX_C_SOURCE=200112L -c -o main.o main.c
main.c:45:45: error: incomplete definition of type 'struct sockaddr_in'
        return &(((struct sockaddr_in *) sa)->sin_addr);
main.c:45:27: note: forward declaration of 'struct sockaddr_in'
        return &(((struct sockaddr_in *) sa)->sin_addr);
main.c:49:42: error: incomplete definition of type 'struct sockaddr_in6'
    return &(((struct sockaddr_in6 *) sa)->sin6_addr);
main.c:49:23: note: forward declaration of 'struct sockaddr_in6'
    return &(((struct sockaddr_in6 *) sa)->sin6_addr);
2 errors generated.
gmake: *** [Makefile:15: main.o] Error 1

Since the MC Server (having the same function) compiled without a
problem, I thought to compare includes between the two `main.c` files
and sure enough, I forgot to include `netinet/in.h` on the client's
Move PORT number to common.h
Describe invalid send code response error
Gather all common stuff between server and client into one file
Remove obsolette append_nick function