--- src/tspi/rpc/tcstp/rpc.c	2010-03-11 12:26:51.000000000 -0800
+++ src/tspi/rpc/tcstp/rpc.c	2012-04-11 14:28:08.181630000 -0700
@@ -345,41 +345,67 @@
 	BYTE *buffer;
 	TSS_RESULT result;
 
-	struct sockaddr_in addr;
-	struct hostent *hEnt = NULL;
+	if (get_port() == 0) { /* use UNIX Domain socket */
+		struct sockaddr_un addr;
 
-	sd = socket(PF_INET, SOCK_STREAM, 0);
-	if (sd == -1) {
-		LogError("socket: %s", strerror(errno));
-		result = TSPERR(TSS_E_COMM_FAILURE);
-		goto err_exit;
-	}
-
-	memset(&addr, 0, sizeof(addr));
-	addr.sin_family = AF_INET;
-	addr.sin_port = htons(get_port());
+		sd = socket(PF_UNIX, SOCK_STREAM, 0);
+		if (sd == -1) {
+			LogError("socket(PF_UNIX): %s", strerror(errno));
+			result = TSPERR(TSS_E_COMM_FAILURE);
+			goto err_exit;
+		}
 
-	LogDebug("Sending TSP packet to host %s.", hte->hostname);
+		memset(&addr, 0, sizeof(addr));
+		addr.sun_family = AF_UNIX;
+		strncpy(addr.sun_path, TCSD_DEFAULT_SOCKET,
+			sizeof(addr.sun_path));
+
+		LogDebug("Connecting to UNIX Domain socket %s",
+			TCSD_DEFAULT_SOCKET);
+
+		if (connect(sd, (struct sockaddr *) &addr, sizeof (addr))) {
+			LogError("connect: %s", strerror(errno));
+			result = TSPERR(TSS_E_COMM_FAILURE);
+			goto err_exit;
+		}
 
-	/* try to resolve by hostname first */
-	hEnt = gethostbyname((char *)hte->hostname);
-	if (hEnt == NULL) {
-		/* if by hostname fails, try by dot notation */
-		if (inet_aton((char *)hte->hostname, &addr.sin_addr) == 0) {
-			LogError("hostname %s does not resolve to a valid address.", hte->hostname);
-			result = TSPERR(TSS_E_CONNECTION_FAILED);
+	} else { /* use TCP socket */
+		struct sockaddr_in addr;
+		struct hostent *hEnt = NULL;
+
+		sd = socket(PF_INET, SOCK_STREAM, 0);
+		if (sd == -1) {
+			LogError("socket: %s", strerror(errno));
+			result = TSPERR(TSS_E_COMM_FAILURE);
 			goto err_exit;
 		}
-	} else {
-		memcpy(&addr.sin_addr, hEnt->h_addr_list[0], 4);
-	}
 
-	LogDebug("Connecting to %s", inet_ntoa(addr.sin_addr));
+		memset(&addr, 0, sizeof(addr));
+		addr.sin_family = AF_INET;
+		addr.sin_port = htons(get_port());
+
+		LogDebug("Sending TSP packet to host %s.", hte->hostname);
+
+		/* try to resolve by hostname first */
+		hEnt = gethostbyname((char *)hte->hostname);
+		if (hEnt == NULL) {
+			/* if by hostname fails, try by dot notation */
+			if (inet_aton((char *)hte->hostname, &addr.sin_addr) == 0) {
+				LogError("hostname %s does not resolve to a valid address.", hte->hostname);
+				result = TSPERR(TSS_E_CONNECTION_FAILED);
+				goto err_exit;
+			}
+		} else {
+			memcpy(&addr.sin_addr, hEnt->h_addr_list[0], 4);
+		}
 
-	if (connect(sd, (struct sockaddr *) &addr, sizeof (addr))) {
-		LogError("connect: %s", strerror(errno));
-		result = TSPERR(TSS_E_COMM_FAILURE);
-		goto err_exit;
+		LogDebug("Connecting to %s", inet_ntoa(addr.sin_addr));
+
+		if (connect(sd, (struct sockaddr *) &addr, sizeof (addr))) {
+			LogError("connect: %s", strerror(errno));
+			result = TSPERR(TSS_E_COMM_FAILURE);
+			goto err_exit;
+		}
 	}
 
 	if (send_to_socket(sd, hte->comm.buf, hte->comm.hdr.packet_size) < 0) {