diff --git a/cmd/agentbbs/main.go b/cmd/agentbbs/main.go
index 0ce1372..5f7e00b 100644
--- a/cmd/agentbbs/main.go
+++ b/cmd/agentbbs/main.go
@@ -1856,6 +1856,10 @@ func validIRCServer(s string) bool {
 				return false
 			}
 		}
+		portNum, err := strconv.Atoi(port)
+		if err != nil || portNum < 1 || portNum > 65535 {
+			return false
+		}
 	}
 	if host == "" || len(host) > 255 {
 		return false
diff --git a/cmd/agentbbs/main_test.go b/cmd/agentbbs/main_test.go
new file mode 100644
index 0000000..46648aa
--- /dev/null
+++ b/cmd/agentbbs/main_test.go
@@ -0,0 +1,26 @@
+package main
+
+import "testing"
+
+func TestValidIRCServerPortRange(t *testing.T) {
+	for _, server := range []string{
+		"irc.example.com",
+		"irc.example.com:1",
+		"irc.example.com:6667",
+		"irc.example.com:65535",
+	} {
+		if !validIRCServer(server) {
+			t.Errorf("validIRCServer(%q) = false, want true", server)
+		}
+	}
+
+	for _, server := range []string{
+		"irc.example.com:0",
+		"irc.example.com:65536",
+		"irc.example.com:99999",
+	} {
+		if validIRCServer(server) {
+			t.Errorf("validIRCServer(%q) = true, want false", server)
+		}
+	}
+}