--- a/rfcal/cmu200/Makefile	Mon Apr 24 00:45:54 2017 +0000
+++ b/rfcal/cmu200/Makefile	Mon Apr 24 01:43:02 2017 +0000
@@ -3,7 +3,7 @@
 PROGS=	fc-cmu200d fc-serscpi
 INSTBIN=/opt/freecalypso/bin
 
-CMU200D_OBJS=	init.o main.o openport.o sercmd.o
+CMU200D_OBJS=	init.o main.o openport.o sercmd.o session.o socket.o
 SERSCPI_OBJS=	openport.o sertool.o
 
 all:	${PROGS}

--- a/rfcal/cmu200/main.c	Mon Apr 24 00:45:54 2017 +0000
+++ b/rfcal/cmu200/main.c	Mon Apr 24 01:43:02 2017 +0000
@@ -27,7 +27,9 @@
 		bind_socket_pathname = argv[3];
 	else
 		bind_socket_pathname = default_socket_pathname;
-
-	/* to be continued */
-	exit(0);
+	create_listener_socket();
+	for (;;) {
+		get_socket_connection();
+		handle_session();
+	}
 }

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rfcal/cmu200/session.c	Mon Apr 24 01:43:02 2017 +0000
@@ -0,0 +1,51 @@
+/*
+ * This module contains the code that handles a single local socket
+ * connection session.
+ */
+
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+
+extern int activesock;
+
+handle_command()
+{
+	char readbuf[256], linebuf[256];
+	int cc, pos;
+
+	for (pos = 0; ; ) {
+		cc = read(activesock, readbuf, sizeof readbuf);
+		if (cc <= 0) {
+			printf("Client program closed connection\n");
+			return(1);
+		}
+		if (pos + cc > sizeof linebuf) {
+			send_socket_response("-Command too long\n");
+			return(1);
+		}
+		bcopy(readbuf, linebuf + pos, cc);
+		pos += cc;
+		if (linebuf[pos-1] == '\n')
+			break;
+	}
+	linebuf[pos-1] = '\0';
+	printf("Client command: %s\n", linebuf);
+	/* actual command handling will go here */
+	return(0);
+}
+
+handle_session()
+{
+	int rc;
+
+	send_socket_response("+CMU200 interface daemon ready\n");
+	for (;;) {
+		rc = handle_command();
+		if (rc)
+			break;
+	}
+	close(activesock);
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/rfcal/cmu200/socket.c	Mon Apr 24 01:43:02 2017 +0000
@@ -0,0 +1,80 @@
+/*
+ * This module handles the local UNIX domain socket interface for fc-cmu200d.
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <stdio.h>
+#include <string.h>
+#include <strings.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+int listener, activesock;
+
+extern char *bind_socket_pathname;
+
+create_listener_socket()
+{
+	/* local socket binding voodoo copied from osmocon */
+	struct sockaddr_un local;
+	unsigned int namelen;
+	int rc;
+
+	listener = socket(AF_UNIX, SOCK_STREAM, 0);
+	if (listener < 0) {
+		perror("socket(AF_UNIX, SOCK_STREAM, 0)");
+		exit(1);
+	}
+
+	local.sun_family = AF_UNIX;
+	strncpy(local.sun_path, bind_socket_pathname, sizeof(local.sun_path));
+	local.sun_path[sizeof(local.sun_path) - 1] = '\0';
+	unlink(local.sun_path);
+
+	/* we use the same magic that X11 uses in Xtranssock.c for
+	 * calculating the proper length of the sockaddr */
+#if defined(BSD44SOCKETS) || defined(__UNIXWARE__)
+	local.sun_len = strlen(local.sun_path);
+#endif
+#if defined(BSD44SOCKETS) || defined(SUN_LEN)
+	namelen = SUN_LEN(&local);
+#else
+	namelen = strlen(local.sun_path) +
+		  offsetof(struct sockaddr_un, sun_path) + 1;
+#endif
+
+	rc = bind(listener, (struct sockaddr *) &local, namelen);
+	if (rc != 0) {
+		perror("bind on local socket");
+		exit(1);
+	}
+	rc = listen(listener, 1);
+	if (rc != 0) {
+		perror("listen");
+		exit(1);
+	}
+	return(0);
+}
+
+get_socket_connection()
+{
+	struct sockaddr_un un_addr;
+	socklen_t len;
+
+	len = sizeof(un_addr);
+	activesock = accept(listener, (struct sockaddr *) &un_addr, &len);
+	if (activesock < 0) {
+		perror("socket accept");
+		exit(1);
+	}
+	printf("Accepted local socket connection\n");
+	return(0);
+}
+
+send_socket_response(str)
+	char *str;
+{
+	write(activesock, str, strlen(str));
+}