make it possible to specify the IP address to bind to

[ostap]

currently all sockets are bound to INADDR_ANY which might be insecure and even problematic in certain environments. this enhancement is to take the IP address to bind to as a command line argument.

[ostap]

since it might take a while to implement this feature for the distributed mode, here is the workaround:

diff --git a/system.c b/system.c
index beb4bc6..bf359a3 100644
--- a/system.c
+++ b/system.c
@@ -358,7 +358,7 @@ extern IO *sys_socket(int *port)
     unsigned int size = sizeof(addr);
     addr.sin_family = AF_INET;
     addr.sin_port = htons(*port);
-    addr.sin_addr.s_addr = INADDR_ANY;
+    addr.sin_addr.s_addr = inet_addr("127.0.0.1");

     if (bind(sfd, (struct sockaddr*) &addr, size) < 0)
         sys_die("sys: cannot bind a socket to port %d\n", *port);