Add the ability to test local port reachability from the world

main.go

@@ -9,6 +9,7 @@ import (
 	"path"
 	"strings"
 	"time"
+	"strconv"
 
 	"github.com/gin-gonic/gin"
 )
@@ -50,6 +51,14 @@ func stringInSlice(a string, list []string) bool {
 	return false
 }
 
+func testRemoteTCPPort(address string) bool {
+	_, err := net.DialTimeout("tcp", address, 3 * time.Second)
+	if err != nil {
+		return false
+	}
+	return true
+}
+
 func mainHandler(c *gin.Context) {
 	fields := strings.Split(c.Params.ByName("field"), ".")
 	ip, err := net.ResolveTCPAddr("tcp", c.Request.RemoteAddr)
@@ -62,6 +71,19 @@ func mainHandler(c *gin.Context) {
 		ip.IP = cfIP
 	}
 
+        if fields[0] == "porttest" {
+		if len(fields) >= 2 {
+			if port, err := strconv.Atoi(fields[1]); err == nil && port > 0 && port <= 65535 {
+				c.String(200, fmt.Sprintln(testRemoteTCPPort(ip.IP.String() + ":" + fields[1])))
+			} else {
+				c.String(400, "Invalid Port Number")
+			}
+		} else {
+			c.String(400, "Need Port")
+		}
+		return
+        }
+
 	c.Set("ip", ip.IP.String())
 	c.Set("port", ip.Port)
 	c.Set("ua", c.Request.UserAgent())