Adding tests and always use brackets in IPV6 addresses

Code also ensures that brackets are properly added when encoding an IPV6 address.

network.go

@@ -0,0 +1,32 @@
+package xmpp
+
+import (
+	"strconv"
+	"strings"
+)
+
+// ensurePort adds a port to an address if none are provided.
+// It handles both IPV4 and IPV6 addresses.
+func ensurePort(addr string, port int) string {
+	// This is an IPV6 address literal
+	if strings.HasPrefix(addr, "[") {
+		// if address has no port (behind his ipv6 address) - add default port
+		if strings.LastIndex(addr, ":") <= strings.LastIndex(addr, "]") {
+			return addr + ":" + strconv.Itoa(port)
+		}
+		return addr
+	}
+
+	// This is either an IPV6 address without bracket or an IPV4 address
+	switch strings.Count(addr, ":") {
+	case 0:
+		// This is IPV4 without port
+		return addr + ":" + strconv.Itoa(port)
+	case 1:
+		// This is IPV$ with port
+		return addr
+	default:
+		// This is IPV6 without port, as you need to use bracket with port in IPV6
+		return "[" + addr + "]:" + strconv.Itoa(port)
+	}
+}