commit 373303723b12dadb32eea2473c0d79db4aa87aae
Author: John Bintz <hello@theindustriousrabbit.com>
Date:   Wed Dec 28 11:34:14 2022 -0500

    add server

diff --git a/server.c b/server.c
new file mode 100644
index 0000000..b3c721e
--- /dev/null
+++ b/server.c
@@ -0,0 +1,210 @@
+/**
+ * Simple bsdsocket.library server for AmigaOS
+ * Copyright 2022 John Bintz
+ * Released under the MIT License
+ * Visit theindustriousrabbit.com for more fun!
+ *
+ * You would not believe how sparse the documentation for
+ * bsdsocket.library is on the Amiga. All this required
+ * digging through documentation on multiple sites, in
+ * multiple forum threads to describe the Amiga quirks
+ * (Amiga code has quirks? who knew!), and required a bunch of
+ * experimentation and resetting the Minimig MiSTer core
+ * and PPP connection to get this working. I tested it
+ * with CodeWatcher and nothing is leaking, so this should
+ * be a (hopefully) good bsdsocket example in C for the Amiga.
+ *
+ * This code is built for SAS/C. Be sure to disable ChkAbort
+ * in the Linker options, otherwise the SAS/C Ctrl-c
+ * handler will take over and screw up server teardown.
+ *
+ * You can use netcat/ncat on another machine to send data
+ * to the running server:
+ *
+ * echo "whoa computers" | netcat 192.168.50.100 8090
+ *
+ */
+
+#include <stdio.h>
+#include <strings.h>
+
+#include <proto/exec.h>
+#include <dos/dos.h>
+
+#include <proto/socket.h>
+#include <arpa/inet.h>
+#include <netinet/in.h>
+
+// socket stuff
+struct Library *SocketBase;
+int serverSocket = -1;
+struct sockaddr_in serverAddress;
+
+#define PORT (8090)
+#define MAX_CONNECTIONS (2)
+
+// data handling
+#define BUFFER_LENGTH (256)
+char buffer [BUFFER_LENGTH];
+int msgSize;
+
+// set up all the global stuff we need, allowing for early exits
+// on failures.
+int setup(void) {
+  const int enable = 1;
+
+  // this works with the most modern MiamiDX
+  if (!(SocketBase = OpenLibrary("bsdsocket.library", 4))) {
+    printf("Can't open socket library\n");
+    return 1;
+  }
+
+  serverSocket = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
+  if (serverSocket < 0) {
+    printf("can't get a socket\n");
+    return 1;
+  }
+
+  // AmiTCP 4.3 SDK does not have SO_REUSEPORT, this is all you get
+  if (setsockopt(
+    serverSocket,
+    SOL_SOCKET,
+    SO_REUSEADDR,
+    // oh c...
+    &enable,
+    sizeof(int)
+   ) < 0) {
+    printf("can't set socket options\n");
+    return 1;
+  }
+
+  return 0;
+}
+
+void teardown(void) {
+  if (serverSocket != -1) {
+
+    shutdown(
+      serverSocket,
+      // SHUT_RDWR, stop all communication both ways
+      2
+    );
+    // double close it to stop the listen as well
+    CloseSocket(serverSocket);
+    CloseSocket(serverSocket);
+  }
+
+  if (SocketBase) {
+    CloseLibrary(SocketBase);
+  }
+}
+
+int startServer(void) {
+  // bind to all addresses on our defined port
+  memset(&serverAddress, 0, sizeof(serverAddress));
+  serverAddress.sin_family = AF_INET;
+  serverAddress.sin_port = htons(PORT);
+  serverAddress.sin_addr.s_addr = htonl(INADDR_ANY);
+
+  if (bind(
+    serverSocket,
+    (struct sockaddr *) &serverAddress,
+    sizeof(serverAddress)
+  ) < 0) {
+    printf("can't bind\n");
+    return 1;
+  }
+
+  if (listen(serverSocket, MAX_CONNECTIONS) < 0) {
+    printf("can't listen\n");
+    return 1;
+  }
+
+  return 0;
+}
+
+void readData(int clientSocket) {
+  do {
+    // keep stomping over the same buffer
+    // ideally we'd take the data out of the buffer and
+    // do something with it.
+    msgSize = recv(clientSocket, buffer, BUFFER_LENGTH, 0);
+
+    if (msgSize <= 0) {
+      printf("End of data\n");
+    } else {
+      printf("Got stuff: %i\n", msgSize);
+      printf("%s\n", buffer);
+    }
+  } while (msgSize == 256);
+  printf("Data received: %s\n", buffer);
+}
+
+int main(void) {
+  // The incoming netcat client
+  int clientSocket;
+  struct sockaddr_in clientAddress;
+  LONG clientLength = sizeof(clientAddress);
+
+  // be able to use WaitSelect
+  int waitSelectResult;
+  fd_set readFDs;
+
+  if (setup() != 0) {
+    teardown();
+    return 1;
+  }
+
+  printf("got socket number %d\n", serverSocket);
+
+  if (startServer() != 0) {
+    teardown();
+    return 1;
+  }
+
+  printf("listening on port %d\n", PORT);
+
+  // just enough to get WaitSelect working
+  // this macro also wants strings.h included
+  FD_ZERO(&readFDs);    ((
+  FD_SET(serverSocket, &readFDs);
+  waitSelectResult = WaitSelect(
+    serverSocket + 1,
+    &readFDs,
+    NULL, NULL, NULL,
+    // other Exec Signals would go here as ORed mp_SigBits
+    NULL
+  );
+
+  // WaitSelect will trap on Ctrl-C for us, and returns -1 if that happens
+  if (waitSelectResult == -1) {
+    printf("ctrl-c\n");
+    teardown();
+    return 1;
+  }
+
+  if (
+    (
+      clientSocket = accept(
+        serverSocket,
+        (struct sockaddr *) &clientAddress,
+        &clientLength
+      )
+    ) < 0
+  ) {
+    printf("can't accept\n");
+    return 1;
+  }
+
+  // note the capitalization difference on Inet_NtoA. the Amiga does
+  // that a lot...
+  printf("connection from %s\n", Inet_NtoA(clientAddress.sin_addr.s_addr));
+
+  readData(clientSocket);
+
+  printf("all done\n");
+
+  teardown();
+
+  return 0;
+}