diff -r a0573014ff4f -r c42949cfdd92 project_files/frontlib/ipcconn.c
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/project_files/frontlib/ipcconn.c	Thu May 31 18:54:40 2012 +0200
@@ -0,0 +1,134 @@
+#include "ipcconn.h"
+#include "logging.h"
+#include "nonblocksockets.h"
+
+#include <SDL_net.h>
+#include <time.h>
+static TCPsocket ipcListenSocket;
+static NonBlockSocket ipcConnSocket;
+
+static uint8_t ipcReadBuffer[256];
+static int ipcReadBufferSize;
+
+void flib_ipcconn_init() {
+	ipcListenSocket = NULL;
+	ipcConnSocket = NULL;
+	ipcReadBufferSize = 0;
+}
+
+void flib_ipcconn_quit() {
+	flib_ipcconn_close();
+}
+
+int flib_ipcconn_listen() {
+	if(ipcListenSocket || ipcConnSocket) {
+		flib_log_e("flib_ipcconn_listen: Already listening or connected.");
+		return -1;
+	}
+	IPaddress addr;
+	addr.host = INADDR_ANY;
+
+	/* SDL_net does not seem to have a way to listen on a random unused port
+	   and find out which port that is, so let's try to find one ourselves. */
+	// TODO: Is socket binding fail-fast on all platforms?
+	srand(time(NULL));
+	rand();
+	for(int i=0; i<1000; i++) {
+		// IANA suggests using ports in the range 49152-65535 for things like this
+		int ipcPort = 49152+(rand()%(65535-49152));
+		SDLNet_Write16(ipcPort, &addr.port);
+		ipcListenSocket = SDLNet_TCP_Open(&addr);
+		if(!ipcListenSocket) {
+			flib_log_w("Failed to start an IPC listening socket on port %i: %s", ipcPort, SDLNet_GetError());
+		} else {
+			flib_log_i("Listening for IPC connections on port %i.", ipcPort);
+			return ipcPort;
+		}
+	}
+	flib_log_e("Unable to find a free port for IPC.");
+	return -1;
+}
+
+void flib_ipcconn_close() {
+	if(ipcListenSocket) {
+		SDLNet_TCP_Close(ipcListenSocket);
+		ipcListenSocket = NULL;
+	}
+	flib_nbsocket_close(&ipcConnSocket);
+	ipcReadBufferSize = 0;
+}
+
+IpcConnState flib_ipcconn_state() {
+	if(ipcConnSocket) {
+		return IPC_CONNECTED;
+	} else if(ipcListenSocket) {
+		return IPC_LISTENING;
+	} else {
+		return IPC_NOT_CONNECTED;
+	}
+}
+
+/**
+ * Receive a single message and copy it into the data buffer.
+ * Returns the length of the received message, -1 when nothing is received.
+ */
+int flib_ipcconn_recv_message(void *data) {
+	flib_ipcconn_tick();
+
+	if(ipcConnSocket) {
+		int size = flib_nbsocket_recv(ipcConnSocket, ipcReadBuffer+ipcReadBufferSize, sizeof(ipcReadBuffer)-ipcReadBufferSize);
+		if(size>=0) {
+			ipcReadBufferSize += size;
+		} else {
+			flib_nbsocket_close(&ipcConnSocket);
+		}
+	}
+
+	int msgsize = ipcReadBuffer[0];
+	if(ipcReadBufferSize > msgsize) {
+		memcpy(data, ipcReadBuffer+1, msgsize);
+		memmove(ipcReadBuffer, ipcReadBuffer+msgsize+1, ipcReadBufferSize-(msgsize+1));
+		ipcReadBufferSize -= (msgsize+1);
+		return msgsize;
+	} else if(!ipcConnSocket && ipcReadBufferSize>0) {
+		flib_log_w("Last message from engine data stream is incomplete (received %u of %u bytes)", ipcReadBufferSize-1, msgsize);
+		ipcReadBufferSize = 0;
+		return -1;
+	} else {
+		return -1;
+	}
+}
+
+int flib_ipcconn_send_message(void *data, size_t len) {
+	flib_ipcconn_tick();
+
+	if(!ipcConnSocket) {
+		flib_log_w("flib_ipcconn_send_message: Not connected.");
+		return -1;
+	}
+	if(len>255) {
+		flib_log_e("Attempt to send too much data to the engine in a single message.");
+		return -1;
+	}
+
+	uint8_t sendbuf[256];
+	sendbuf[0] = len;
+	memcpy(sendbuf+1, data, len);
+	if(flib_nbsocket_blocksend(ipcConnSocket, sendbuf, len+1) < len+1) {
+		flib_log_w("Failed or incomplete ICP write: engine connection lost.");
+		flib_nbsocket_close(&ipcConnSocket);
+		return -1;
+	} else {
+		return 0;
+	}
+}
+
+void flib_ipcconn_tick() {
+	if(!ipcConnSocket && ipcListenSocket) {
+		ipcConnSocket = flib_nbsocket_accept(ipcListenSocket, true);
+		if(ipcConnSocket) {
+			SDLNet_TCP_Close(ipcListenSocket);
+			ipcListenSocket = NULL;
+		}
+	}
+}