net: TCP sockets in the kernel - a Game Boy fetches HTTP over real TCP

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.

1 files changed, 42 insertions, 14 deletions

diff --git a/c/wget.c b/c/wget.c
index 013b326..9d99eb0 100644
--- a/c/wget.c
+++ b/c/wget.c
@@ -1,18 +1,46 @@
-#include "netlib.h"
-/* wget URL : send the URL to the host gateway over SLIP, print the reply body.
-   The gateway does the real DNS/TCP/HTTP and streams the body back as frames:
-   each reply frame is 'D'<chunk>, ending with a single 'E' frame. */
+#include "sock.h"
+/* wget [A.B.C.D] - fetch http://TARGET/ over the kernel TCP socket layer and
+   print it. No SLIP/IP/TCP here: connect() handshakes in the kernel, send()/
+   recv() drive the stream. Default target 10.0.0.1:80 (the SLIP peer/host). */
+
+static unsigned char buf[220];        /* first + large so dst[] lands arg-safe */
+static unsigned char dst[4];
+
+static unsigned char parse_ip(char *s, unsigned char *out) {
+    unsigned char i, v;
+    for (i = 0; i < 4; i++) {
+        if (*s < '0' || *s > '9') return 0;
+        v = 0;
+        while (*s >= '0' && *s <= '9') { v = (unsigned char)(v * 10 + (*s - '0')); s++; }
+        out[i] = v;
+        if (i < 3) { if (*s != '.') return 0; s++; }
+    }
+    return 1;
+}
+
 void main(void) {
-    char *argv[4];
-    unsigned char argc = argv_parse(argv, 4);
-    char buf[220];
-    unsigned char len, i;
-    if (argc < 1) { puts("usage: wget URL"); nl(); return; }
-    slip_send(argv[0], strlen(argv[0]));
+    char *arg, *r;
+    unsigned char s, n, i;
+    arg = getargs();
+    if (!arg || !*arg) { dst[0] = 10; dst[1] = 0; dst[2] = 0; dst[3] = 1; }
+    else if (!parse_ip(arg, dst)) { puts("wget: bad address"); nl(); sexit(1); }
+
+    s = net_socket(SOCK_TCP);
+    if (s == 0xFF) { puts("wget: no socket"); nl(); sexit(1); }
+    net_bind(s, 40001);
+    puts("connecting"); nl();
+    if (net_connect(s, dst, 80) == 0xFF) { puts("wget: connect failed"); nl(); net_close(s); sexit(1); }
+
+    r = "GET / HTTP/1.0\r\nHost: gbos\r\n\r\n";
+    n = 0;
+    while (r[n]) { buf[n] = r[n]; n++; }
+    net_send(s, buf, n);
+
     for (;;) {
-        len = slip_recv(buf, 219);
-        if (len >= 1 && buf[0] == 'E') break;      /* end of stream */
-        for (i = 1; i < len; i++) putc(buf[i]);    /* skip the 'D' type byte */
+        n = net_recv(s, buf, (unsigned char)sizeof(buf));
+        if (n == 0xFF) { nl(); puts("[timeout]"); nl(); break; }
+        if (n == 0)    { nl(); puts("[eof]");     nl(); break; }
+        for (i = 0; i < n; i++) putc((char)buf[i]);
     }
-    nl();
+    net_close(s);
 }