diff --git a/contrib/netcat/nc.1 b/contrib/netcat/nc.1
--- a/contrib/netcat/nc.1
+++ b/contrib/netcat/nc.1
@@ -27,7 +27,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd January 20, 2025
+.Dd May 14, 2025
 .Dt NC 1
 .Os
 .Sh NAME
@@ -351,8 +351,8 @@
 option is given).
 .Pp
 .Ar port
-can be a single integer or a range of ports.
-Ranges are in the form nn-mm.
+can be a specified as a numeric port number, or as a service name.
+Ports may be specified in a range of the form nn-mm.
 In general,
 a destination port must be specified,
 unless the
diff --git a/contrib/netcat/netcat.c b/contrib/netcat/netcat.c
--- a/contrib/netcat/netcat.c
+++ b/contrib/netcat/netcat.c
@@ -119,6 +119,7 @@
 char *unix_dg_tmp_socket;
 
 void	atelnet(int, unsigned char *, unsigned int);
+int	strtoport(char *portstr, int udp);
 void	build_ports(char *);
 void	help(void);
 int	local_listen(char *, char *, struct addrinfo);
@@ -1197,6 +1198,26 @@
 	}
 }
 
+int
+strtoport(char *portstr, int udp)
+{
+	struct servent *entry;
+	const char *errstr;
+	char *proto;
+	int port = -1;
+
+	proto = udp ? "udp" : "tcp";
+
+	port = strtonum(portstr, 1, PORT_MAX, &errstr);
+	if (errstr == NULL)
+		return port;
+	if (errno != EINVAL)
+		errx(1, "port number %s: %s", errstr, portstr);
+	if ((entry = getservbyname(portstr, proto)) == NULL)
+		errx(1, "service \"%s\" unknown", portstr);
+	return ntohs(entry->s_port);
+}
+
 /*
  * build_ports()
  * Build an array of ports in portlist[], listing each port
@@ -1205,7 +1226,6 @@
 void
 build_ports(char *p)
 {
-	const char *errstr;
 	char *n;
 	int hi, lo, cp;
 	int x = 0;
@@ -1215,46 +1235,39 @@
 		n++;
 
 		/* Make sure the ports are in order: lowest->highest. */
-		hi = strtonum(n, 1, PORT_MAX, &errstr);
-		if (errstr)
-			errx(1, "port number %s: %s", errstr, n);
-		lo = strtonum(p, 1, PORT_MAX, &errstr);
-		if (errstr)
-			errx(1, "port number %s: %s", errstr, p);
-
+		hi = strtoport(n, uflag);
+		lo = strtoport(p, uflag);
 		if (lo > hi) {
 			cp = hi;
 			hi = lo;
 			lo = cp;
 		}
 
-		/* Load ports sequentially. */
-		for (cp = lo; cp <= hi; cp++) {
-			portlist[x] = calloc(1, PORT_MAX_LEN);
-			if (portlist[x] == NULL)
-				err(1, NULL);
-			snprintf(portlist[x], PORT_MAX_LEN, "%d", cp);
-			x++;
-		}
-
-		/* Randomly swap ports. */
+		/*
+		 * Initialize portlist with a random permutation.  Based on
+		 * Knuth, as in ip_randomid() in sys/netinet/ip_id.c.
+		 */
 		if (rflag) {
-			int y;
-			char *c;
-
-			for (x = 0; x <= (hi - lo); x++) {
-				y = (arc4random() & 0xFFFF) % (hi - lo);
-				c = portlist[x];
-				portlist[x] = portlist[y];
-				portlist[y] = c;
+			for (x = 0; x <= hi - lo; x++) {
+				cp = arc4random_uniform(x + 1);
+				portlist[x] = portlist[cp];
+				if (asprintf(&portlist[cp], "%d", x + lo) == -1)
+					err(1, "asprintf");
+			}
+		} else { /* Load ports sequentially. */
+			for (cp = lo; cp <= hi; cp++) {
+				if (asprintf(&portlist[x], "%d", cp) == -1)
+					err(1, "asprintf");
+				x++;
 			}
 		}
 	} else {
-		hi = strtonum(p, 1, PORT_MAX, &errstr);
-		if (errstr)
-			errx(1, "port number %s: %s", errstr, p);
-		portlist[0] = strdup(p);
-		if (portlist[0] == NULL)
+		char *tmp;
+
+		hi = strtoport(p, uflag);
+		if (asprintf(&tmp, "%d", hi) != -1)
+			portlist[0] = tmp;
+		else
 			err(1, NULL);
 	}
 }