diff -uw ucspi-tcp-0.88-original/tcpclient.c ucspi-tcp-0.88/tcpclient.c
--- ucspi-tcp-0.88-original/tcpclient.c	2000-03-18 15:18:42.000000000 +0000
+++ ucspi-tcp-0.88/tcpclient.c	2004-11-12 17:25:50.000000000 +0000
@@ -65,6 +65,17 @@
 
 char seed[128];
 
+static
+void
+optarg_num ( unsigned long * u )
+{
+  unsigned int pos ;
+  pos = scan_ulong(optarg,u); 
+  if (0 == pos || optarg[pos])
+    strerr_die3x(111,FATAL, optarg, " is not a number");
+}
+
+int
 main(int argc,char **argv)
 {
   unsigned long u;
@@ -92,13 +103,20 @@
       case 'h': flagremotehost = 1; break;
       case 'R': flagremoteinfo = 0; break;
       case 'r': flagremoteinfo = 1; break;
-      case 't': scan_ulong(optarg,&itimeout); break;
+      case 't': optarg_num(&itimeout); break;
       case 'T': j = scan_ulong(optarg,&ctimeout[0]);
-		if (optarg[j] == '+') ++j;
-		scan_ulong(optarg + j,&ctimeout[1]);
+		if (optarg[j] == '+') {
+		  unsigned int k ;
+		  ++j;
+		  k = scan_ulong(optarg + j,&ctimeout[1]);
+		  if (0 == k || optarg[j + k]) strerr_die3x(111,FATAL, optarg + j, " is not a number");
+		} else 
+		  if (0 == j || optarg[j]) strerr_die3x(111,FATAL, optarg, " is not a number");
+		break;
+      case 'i': j = ip4_scan(optarg,iplocal); 
+		if (0 == j || optarg[j]) strerr_die3x(111,FATAL, optarg, " is not an IP address");
 		break;
-      case 'i': if (!ip4_scan(optarg,iplocal)) usage(); break;
-      case 'p': scan_ulong(optarg,&u); portlocal = u; break;
+      case 'p': optarg_num(&u); portlocal = u; break;
       default: usage();
     }
   argv += optind;
diff -uw ucspi-tcp-0.88-original/tcpserver.c ucspi-tcp-0.88/tcpserver.c
--- ucspi-tcp-0.88-original/tcpserver.c	2000-03-18 15:18:42.000000000 +0000
+++ ucspi-tcp-0.88/tcpserver.c	2004-11-12 17:25:56.000000000 +0000
@@ -289,6 +289,17 @@
   }
 }
 
+static
+void
+optarg_num ( unsigned long * u )
+{
+  unsigned int pos ;
+  pos = scan_ulong(optarg,u); 
+  if (0 == pos || optarg[pos])
+    strerr_die3x(111,FATAL, optarg, " is not a number");
+}
+
+int
 main(int argc,char **argv)
 {
   char *hostname;
@@ -302,8 +313,8 @@
  
   while ((opt = getopt(argc,argv,"dDvqQhHrR1UXx:t:u:g:l:b:B:c:pPoO")) != opteof)
     switch(opt) {
-      case 'b': scan_ulong(optarg,&backlog); break;
-      case 'c': scan_ulong(optarg,&limit); break;
+      case 'b': optarg_num(&backlog); break;
+      case 'c': optarg_num(&limit); break ;
       case 'X': flagallownorules = 1; break;
       case 'x': fnrules = optarg; break;
       case 'B': banner = optarg; break;
@@ -320,11 +331,11 @@
       case 'h': flagremotehost = 1; break;
       case 'R': flagremoteinfo = 0; break;
       case 'r': flagremoteinfo = 1; break;
-      case 't': scan_ulong(optarg,&timeout); break;
+      case 't': optarg_num(&timeout); break;
       case 'U': x = env_get("UID"); if (x) scan_ulong(x,&uid);
 		x = env_get("GID"); if (x) scan_ulong(x,&gid); break;
-      case 'u': scan_ulong(optarg,&uid); break;
-      case 'g': scan_ulong(optarg,&gid); break;
+      case 'u': optarg_num(&uid); break;
+      case 'g': optarg_num(&gid); break;
       case '1': flag1 = 1; break;
       case 'l': localhost = optarg; break;
       default: usage();