libvncclient: add a non-forking listen function.

Forking the whole process from deep within a library call does
not really work at all with apps that use multiple threads, i.e. every
reasonably modern GUI app. So, provide a non-forking listen function so
that the caller can decide if to fork, start a thread, etc.

This implementation adds a timeout parameter to be able to call the
listen function multiple times so that it's possible to do sth. else
in between, e.g. abort listening.

Signed-off-by: Christian Beier <dontmind@freeshell.org>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>

3 files changed, 65 insertions, 0 deletions

diff --git a/libvncclient/listen.c b/libvncclient/listen.c
index 7347a27..d1e98ae 100644
--- a/libvncclient/listen.c
+++ b/libvncclient/listen.c
@@ -27,6 +27,7 @@
 #include <unistd.h>
 #include <sys/types.h>
 #ifdef __MINGW32__
+#define close closesocket
 #include <winsock2.h>
 #else
 #include <sys/wait.h>
@@ -108,3 +109,59 @@ listenForIncomingConnections(rfbClient* client)
 }
 
 
+
+/*
+ * listenForIncomingConnectionsNoFork() - listen for incoming connections
+ * from servers, but DON'T fork, instead just wait timeout microseconds.
+ * If timeout is negative, block indefinitly.
+ */
+
+rfbBool
+listenForIncomingConnectionsNoFork(rfbClient* client, int timeout)
+{
+  fd_set fds;
+  struct timeval to;
+
+  to.tv_sec= timeout / 1000000;
+  to.tv_usec= timeout % 1000000;
+
+  client->listenSpecified = TRUE;
+
+  if (! client->listenSock)
+    {
+      client->listenSock = ListenAtTcpPort(client->listenPort);
+
+      if (client->listenSock < 0)
+	return FALSE;
+
+      rfbClientLog("%s -listennofork: Listening on port %d\n",
+		   client->programName,client->listenPort);
+      rfbClientLog("%s -listennofork: Command line errors are not reported until "
+		   "a connection comes in.\n", client->programName);
+    }
+
+  FD_ZERO(&fds);
+
+  FD_SET(client->listenSock, &fds);
+
+  if (timeout < 0)
+    select(FD_SETSIZE, &fds, NULL, NULL, NULL);
+  else
+    select(FD_SETSIZE, &fds, NULL, NULL, &to);
+
+  if (FD_ISSET(client->listenSock, &fds))
+    {
+      client->sock = AcceptTcpConnection(client->listenSock);
+      if (client->sock < 0)
+	return FALSE;
+      if (!SetNonBlocking(client->sock))
+	return FALSE;
+
+      close(client->listenSock);
+      return TRUE;
+    }
+
+  return FALSE;
+}
+
+
diff --git a/libvncclient/vncviewer.c b/libvncclient/vncviewer.c
index 7e678fb..f29bd5f 100644
--- a/libvncclient/vncviewer.c
+++ b/libvncclient/vncviewer.c
@@ -43,6 +43,7 @@ static void DummyRect(rfbClient* client, int x, int y, int w, int h) {
 static char* NoPassword(rfbClient* client) {
   return strdup("");
 }
+#define close closesocket
 #else
 #include <stdio.h>
 #include <termios.h>
@@ -247,6 +248,9 @@ rfbBool rfbInitClient(rfbClient* client,int* argc,char** argv) {
       if (strcmp(argv[i], "-listen") == 0) {
 	listenForIncomingConnections(client);
 	break;
+      } else if (strcmp(argv[i], "-listennofork") == 0) {
+	listenForIncomingConnectionsNoFork(client, -1);
+	break;
       } else if (strcmp(argv[i], "-play") == 0) {
 	client->serverPort = -1;
 	j++;
diff --git a/rfb/rfbclient.h b/rfb/rfbclient.h
index 40c1775..aa9d2e4 100644
--- a/rfb/rfbclient.h
+++ b/rfb/rfbclient.h
@@ -151,6 +151,9 @@ typedef struct _rfbClient {
 	rfbPixelFormat format;
 	rfbServerInitMsg si;
 
+	/* listen.c */
+        int listenSock;
+
 	/* sockets.c */
 #define RFB_BUF_SIZE 8192
 	char buf[RFB_BUF_SIZE];
@@ -260,6 +263,7 @@ extern rfbBool HandleCursorShape(rfbClient* client,int xhot, int yhot, int width
 /* listen.c */
 
 extern void listenForIncomingConnections(rfbClient* viewer);
+extern rfbBool listenForIncomingConnectionsNoFork(rfbClient* viewer, int usec_timeout);
 
 /* rfbproto.c */