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Userland sources live in usr/ (fits the Unix theme better than 'c').
SDCC output .bin blobs land in build/usr/ with the other build artifacts
instead of littering the source dir; programs.asm INCBINs them from there.
Byte-identical ROM.
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resolve.h: shared helper that turns a dotted-quad or a hostname into an IPv4
address (DNS A query over a UDP socket to 1.1.1.1). nslookup now uses it and
slims down; wget uses it so you can name a host directly.
wget HOST|IP now: resolve -> TCP connect -> "GET / HTTP/1.0" with the real
Host header -> stream the body to the LCD/console until EOF. One command does
DNS + TCP + HTTP, all on the kernel socket layer.
Verified over tunbridge's NAT against the real internet:
/# wget example.com
connecting 172.66.147.243
HTTP/1.1 200 OK
Server: cloudflare
<!doctype html><html lang="en"><head><title>Example Domain</title>...
</body></html>
[eof]
The full HTML page arrives across many TCP segments and is reassembled and
printed - real DNS, real TCP, real HTTP, fetched by a Game Boy by name.
(tunbridge.py already sets up + tears down the NAT, so the demo is a one-liner:
sudo python3 tools/tunbridge.py "wget example.com")
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Kernel TCP client on the socket layer: net_connect(SOCK_TCP) runs the 3-way
handshake in-kernel, send()/recv() drive the byte stream, close() does the FIN.
- Socket gains state + 32-bit snd_nxt/rcv_nxt (big-endian, add-with-carry-fold).
- tcp_send_seg builds IP+TCP with a pseudo-header checksum; the SYN carries an
MSS option (200) so the peer never sends a segment larger than our 256-byte
frame buffer (we don't do IP reassembly).
- tcp_in state machine: SYN_SENT->ESTABLISHED on SYN-ACK, buffers in-order data
and ACKs it, handles FIN -> recv() returns 0 (EOF).
- No retransmission: the GB<->host link is lossless and the host's real TCP
owns the internet side - which removes TCP's hardest part.
- net_pump now processes one frame per call so recv drains each segment before
the next arrives (single rx slot, no overwrite).
wget.c is now a thin socket client: connect -> send "GET / HTTP/1.0" -> recv to
EOF -> print. Verified end to end against a host HTTP server:
/# wget 10.0.0.1
HTTP/1.0 200 OK
Hello from a real HTTP server, fetched by a Game Boy!
with a clean SYN/SYN-ACK/ACK ... PSH ... FIN/ACK trace on the wire.
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Grow the link-port demo from echo to actual network access. The Game Boy
still only does SLIP framing + display; the host gateway does DNS/TCP/HTTP.
- c/netlib.h: SLIP framing factored out (header-only, per-program copy).
necho.c now uses it too.
- c/wget.c: `wget URL` frames the URL, then prints the reply body. The
gateway streams the body back as typed frames: 'D'<chunk> ... 'E'.
- tools/gateway.py: add --mode http (urlopen the frame as a URL, cap the
body, chunk it) alongside --mode echo; --cmd runs any gbos command.
Verified: `wget example.com` streams back the full Example Domain HTML onto
the terminal; `wget sl0p.foo` fetches the real page. A Game Boy on the web,
over the link cable.
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