Use a constant for PortSpecTemplate + display the template in the CmdRun help

commands.go

@@ -1762,10 +1762,11 @@ func parseRun(cmd *flag.FlagSet, args []string, capabilities *Capabilities) (*Co
 		_ = cmd.Bool("sig-proxy", true, "Proxify all received signal to the process (even in non-tty mode)")
 		_ = cmd.String("name", "", "Assign a name to the container")
 	)
+
 	cmd.Var(flAttach, "a", "Attach to stdin, stdout or stderr.")
 	cmd.Var(flVolumes, "v", "Bind mount a volume (e.g. from the host: -v /host:/container, from docker: -v /container)")
 
-	cmd.Var(&flPublish, "p", "Publish a container's port to the host (use 'docker port' to see the actual mapping)")
+	cmd.Var(&flPublish, "p", fmt.Sprintf("Publish a container's port to the host (format: %s) (use 'docker port' to see the actual mapping)", PortSpecTemplateFormat))
 	cmd.Var(&flExpose, "expose", "Expose a port from the container without publishing it to your host")
 	cmd.Var(&flEnv, "e", "Set environment variables")
 	cmd.Var(&flDns, "dns", "Set custom dns servers")

utils.go

@@ -206,6 +206,12 @@ func parseLxcOpt(opt string) (string, string, error) {
 	return strings.TrimSpace(parts[0]), strings.TrimSpace(parts[1]), nil
 }
 
+// FIXME: network related stuff (including parsing) should be grouped in network file
+const (
+	PortSpecTemplate       = "ip:hostPort:containerPort"
+	PortSpecTemplateFormat = "ip:hostPort:containerPort | ip::containerPort | hostPort:containerPort"
+)
+
 // We will receive port specs in the format of ip:public:private/proto and these need to be
 // parsed in the internal types
 func parsePortSpecs(ports []string) (map[Port]struct{}, map[Port][]PortBinding, error) {
@@ -227,7 +233,7 @@ func parsePortSpecs(ports []string) (map[Port]struct{}, map[Port][]PortBinding,
 			rawPort = fmt.Sprintf(":%s", rawPort)
 		}
 
-		parts, err := utils.PartParser("ip:hostPort:containerPort", rawPort)
+		parts, err := utils.PartParser(PortSpecTemplate, rawPort)
 		if err != nil {
 			return nil, nil, err
 		}