Add endopoint to check is a given port is open on the client (#22)

router/port_scanner.go

@@ -0,0 +1,54 @@
+package router
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"strconv"
+
+	"github.com/dcarrillo/whatismyip/service"
+	"github.com/gin-gonic/gin"
+)
+
+type JSONScanResponse struct {
+	IP        string `json:"ip"`
+	Port      int    `json:"port"`
+	Reachable bool   `json:"reachable"`
+	Reason    string `json:"reason"`
+}
+
+func scanTCPPort(ctx *gin.Context) {
+	port, err := strconv.Atoi(ctx.Params.ByName("port"))
+	if err == nil && (port < 1 || port > 65535) {
+		err = fmt.Errorf("%d is not a valid port number", port)
+	}
+	if err != nil {
+		ctx.JSON(http.StatusBadRequest, JSONScanResponse{
+			Reason: err.Error(),
+		})
+		return
+	}
+
+	add := net.TCPAddr{
+		IP:   net.ParseIP(ctx.ClientIP()),
+		Port: port,
+	}
+
+	scan := service.PortScanner{
+		Address: &add,
+	}
+
+	isOpen, err := scan.IsPortOpen()
+	reason := ""
+	if err != nil {
+		reason = err.Error()
+	}
+
+	response := JSONScanResponse{
+		IP:        ctx.ClientIP(),
+		Port:      port,
+		Reachable: isOpen,
+		Reason:    reason,
+	}
+	ctx.JSON(http.StatusOK, response)
+}

router/setup.go

@@ -22,6 +22,7 @@ func SetupTemplate(r *gin.Engine) {
 // Setup defines the endpoints
 func Setup(r *gin.Engine) {
 	r.GET("/", getRoot)
+	r.GET("/scan/tcp/:port", scanTCPPort)
 	r.GET("/client-port", getClientPortAsString)
 	r.GET("/geo", getGeoAsString)
 	r.GET("/geo/:field", getGeoAsString)