--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/mncc/mncc_sock.c	Sun Jun 26 16:31:47 2022 -0800
@@ -0,0 +1,63 @@
+/*
+ * In this module we implement low-level handling
+ * of the main MNCC socket that connects to OsmoMSC.
+ */
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <stdio.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <syslog.h>
+#include "../include/mncc.h"
+
+static char mncc_socket_pathname[] = "/var/gsm/mncc_socket";
+
+int mncc_socket;
+
+open_mncc_socket()
+{
+	struct sockaddr_un sa;
+	unsigned sa_len;
+	int rc;
+
+	mncc_socket = socket(AF_UNIX, SOCK_SEQPACKET, 0);
+	if (mncc_socket < 0) {
+		syslog(LOG_CRIT, "socket(AF_UNIX, SOCK_SEQPACKET, 0): %m");
+		return(-1);
+	}
+	fill_sockaddr_un(mncc_socket_pathname, &sa, &sa_len);
+	rc = connect(mncc_socket, (struct sockaddr *) &sa, sa_len);
+	if (rc < 0) {
+		syslog(LOG_ERR, "connect to %s: %m", mncc_socket_pathname);
+		return(-1);
+	}
+	update_max_fd(mncc_socket);
+	return(0);
+}
+
+void
+mncc_socket_select()
+{
+	union mncc_msg msg;
+	int rc;
+
+	rc = recv(mncc_socket, &msg, sizeof msg, 0);
+	if (rc < 0) {
+		syslog(LOG_CRIT, "error reading from MNCC socket: %m");
+		exit(1);
+	}
+	if (rc < 4) {
+		syslog(LOG_CRIT, "short read from MNCC socket: %d bytes", rc);
+		exit(1);
+	}
+	mncc_msg_from_gsm(&msg, rc);
+}
+
+send_mncc_to_gsm(msg, msglen)
+	union mncc_msg *msg;
+	unsigned msglen;
+{
+	return send(mncc_socket, msg, msglen, 0);
+}