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FAQ

General

Q: How to start?

To use SSTP Connect, you need to create a profile first.

These items are needed for a profile:

• A description of the connection
• Server address
• Username and password (or certificate)
• Virtual Hub name (SoftEther only)

If you have an existing connection setting file (.vpn) from SoftEther VPN Client Manager, you can import it as a new profile by:

• clicking + and choose Import From File, or
• opening / sharing the file to the app.

Q: What are the items in a profile and what do they mean?

• Protocol

  Select the VPN protocol you want to use. We currently support SSTP and SoftEther.

• Description

  Required

  Fill in anything that helps you to identify the connection. It will also become the name shown in the system VPN list.

• Server

  Required

  VPN server address in either hostname or IP address.

  Generally you should use a hostname (e.g. vpn.example.com), so that you don't need to take care of IP changes.

  However, if your DNS provider is unreliable, or you want to enforce connecting via IPv4 or IPv6 (if the server is dual-stack), you can use an IP address instead.

  System proxy will automatically be used in iOS 12 and above.

• Hostname

  Server hostname that will be used in the TLS server trust evaluation.

  If you entered a hostname in the server field, you don't need to fill in the same hostname again.

  If you entered an IP address in the server field, please fill in the hostname here that matches the server certificate, otherwise TLS validation will fail.

• Port

  Port number of the server. By default it's 443.

• TLS Server Trust Evaluation

  TLS validation verifies the server's identity and protects you from MITM (man-in-the-middle) attacks. We STRONGLY RECOMMEND you enable it at all times.

  If the server uses non-public certificates, additional steps may be needed to pass TLS validation. See below for more information.

• Virtual Hub

  SoftEther only

  Enter the Virtual Hub name.

  The common default hub names are default and vpn. If you are using VPN Gate service, the hub name is vpngate.

• Connections

  SoftEther only

  The number of TCP connections for a SoftEther VPN session.

  We support 32 connections at most but you are recommended to start from 2. More connections consume more memory. Do not use under heavy load.

• UDP Acceleration

  SoftEther only

  Whether to enable the UDP acceleration feature.

  Available in iOS 13+ and SoftEther Server 4.30+.

• Authentication Method

  Choose either password or certificate.

  Authentication with certificate is supported in iOS 12 and above.

• Username

  Required

  Fill in the account name of the VPN.

  For SSTP users with certificate-based authentication, username can be omitted if it matches the certificate's User Principal Name (UPN).

  For SoftEther users connecting with SSTP protocol, the Virtual Hub name should be appended to the account in the form user@HUB, unless the default Virtual Hub is being used.

• Password

  Fill in your password. Passwords are saved in the keychain, protected by iOS.

  If nothing is entered, you will be asked for the password upon connecting.

• Certificate

  Required for certificate-based authentication

  Import and select the certificate you want to use. Certificates (including private keys) are saved in the keychain, protected by iOS.

  See below for how to import certificates. SoftEther protocol accepts RSA certificates only.

• Enable EAP-MSCHAPv2

  SSTP only

  Enable if the server requires EAP-MSCHAPv2 for password authentication.

• Enable PAP / CHAP

  SSTP only

  Enable if the server only supports these obsolete authentication methods.

• Tunnel IP Version

  Choose the IP version inside the VPN tunnel. For IPv6 tunnels, only stateless configuration is currently supported (DHCPv6 not supported).

• Static IP / DNS

  Specify manual IP and DNS settings if instructed by your administrator.

• MTU

  Tunnel MTU size. By default it's 1400 for SSTP or 1500 for SoftEther.

  Generally it has little to do with the client's network environment and does not need to be changed.

• Add Default Route

  Select whether to add the default route so that Internet traffic will be routed via VPN.

  In iOS built-in VPN the option is called Send All Traffic.

• Proxy

  Specify the proxy settings inside the VPN tunnel.

• On Demand Rules

  Edit VPN On Demand rules. See below for more information.

• Disable TLS 1.0 & 1.1

  TLS 1.0 and 1.1 are obsolete versions. The app will use the highest TLS version (up to 1.3) that the server accepts. But you can also explicitly disable these old versions here.

• Auto Reconnect

  Select whether to reconnect the VPN if interrupted.

• Retry Times

  Number of times to retry if the connection fails.

• Temporary IPv6 Address

  Use temporary IPv6 addresses every time connected if allowed by the server. If disabled, the same IPv6 address will be used for a profile.

• Switch to Wi-Fi When Available

  When an existing VPN session is on mobile network and the device connects to Wi-Fi, by default the session will stay on mobile. Enable this option to allow upgrading to Wi-Fi.

  Note that the upgrade is controlled by iOS and might not always work. For example, if the current mobile connection is made over IPv6 but the Wi-Fi is IPv4 only, there is chance that the upgrade will not occur.

• Stay Connected During Sleep

  Choose whether to disconnect the VPN as the device goes to sleep.

  Disabling the option saves battery but reconnection may take some time.

  Even with the option set to on, the VPN is not guaranteed to survive a sleep as the sleep and wake-up is handled by iOS. In particular we have noticed that when both mobile data and WiFi is on, connections over WiFi may not stay on during sleep. Switching off mobile data may help.

Q: Can I connect or disconnect via system VPN settings?

Yes, you can. Your profiles are saved in the system with your credentials in the keychain. Therefore, you can connect and disconnect the VPN without opening the app.

TLS Server Trust Evaluation (TLS Validation)

Q: What requirements should a server certificate meet in order to pass TLS validation?

iOS has implemented more strict rules on server certificates since iOS 13. See below links for more information.

https://support.apple.com/en-us/HT210176

https://support.apple.com/en-us/HT211025

The most important requirements are:

• RSA key size must be at least 2048 bits
• Hash algorithm should be in the SHA-2 family (such as SHA256)
• DNS name should be presented in Subject Alternative Name (SAN) (Common Name is no longer used)
• Validity period must be 825 days or fewer

Q: What should I do if I want to use certificates generated by SoftEther VPN Server?

Certificates automatically generated by SoftEther VPN Server do not meet the above requirements. Please follow this guide to regenerate.

Q: What should I do if the server uses a self-signed certificate or a certificate not signed by a public CA?

For security reasons, certificates signed by public CAs should be used. However if that’s not possible, you can ask your administrator for the root CA certificate and both install and trust it on your device.

Note that the certificate still needs to meet the above requirements.

Q: How to install and trust a certificate?

Email the certificate to yourself or download it from the web, then open it on your device. iOS should prompt you that a profile is now ready to install.

To install it: https://support.apple.com/en-us/HT209435

To trust it: https://support.apple.com/en-us/HT204477

Q: Can I disable TLS validation?

Generally speaking, you should never disable TLS validation. However, in some circumstances you may want to do so (e.g. the server uses an obsolete or weak certificate and you can’t change it).

Only use it as the last resort and always consult your administrator first.

Authentication with Certificates

Q: How to import my certificates?

The first step of using certificate-based authentication is importing your certificates. Currently the app only accepts certificates packed in PKCS #12 format (.p12 or .pfx files).

PKCS #12 is the default format on Windows platform and also supported by SoftEther VPN Server.

You need to obtain the P12 file from your administrator and place it on your device. This can be done in several ways:

• Via Finder or iTunes File Sharing on a computer (see links below)
• Email the file to yourself, long press the attachment and choose Save to Files
• Save in iCloud Drive or other cloud drive that can be accessed by the Files app

When the certificate is on your device, import it into the app by tapping Import and navigate to the folder. You need to enter the password and give the certificate a distinct description.

The certificate (and its private key) will be saved in the keychain. For security reasons, please delete the file after import or keep it in a secure place.

A certificate can be used by multiple profiles.

Guide on using the Finder to share files from a computer

For macOS Catalina or later

https://support.apple.com/en-us/HT210598

Guide on using iTunes to share files from a computer

For macOS Mojave or earlier or a Windows PC

https://support.apple.com/en-us/HT201301

Q: How to remove a certificate?

In Select Certificate, you can swipe to remove certificates.

Note that under current iOS, if you remove the app without removing all the certificates, they may still be kept in the keychain (Don't worry. They are always protected by iOS). Once you reinstall the app, you can use them again.

Q: I want to import a new certificate but the app complains it's already in the keychain. How is that possible?

According to iOS policy, certificates with the same serial number from the same issuer are considered the same, even if the names are different. Please ask the administrator to generate the certificate with a new serial number.

Q: I have certificates installed in the system. Why can't I see them in the app?

As a third-party app, we can't access certificates installed in the system like built-in VPN does. You have to import them using the app.

VPN On Demand

Q: What is VPN On Demand and how to use it?

VPN On Demand is an advanced iOS feature that allows a VPN connection to be connected / disconnected if some rule matches.

You must first define a set of rules. iOS will try to match them in order and only the first matched rule will be applied. The matching process is completely handled by iOS and the app has no way to alter the behavior.

Important: Only the rules of the current enabled (selected) VPN profile are assessed.

Q: How to write an on demand rule?

A rule has one action and a number of conditions. If all conditions are met, the action is taken.

There are four types of actions:

• Connect
• Disconnect
• Evaluate Connection (see below)
• Ignore

You can specify these types of conditions:

• Current Interface Type (Wi-Fi, Cellular, or any)
• Wi-Fi SSID (multiple allowed)
• DNS Search Domain (multiple allowed)
• DNS Servers (multiple allowed)
• Probe URL (matches if the specified HTTP or HTTPS URL can be reached)

If no condition is specified, the rule matches all situations and any rule after it will never be matched.

Q: If I want the VPN to be connected when I am away from a WiFi network but disconnected on that network, how should I setup the rules?

You need to create two rules in the following order.

• Rule 1

  Action: Disconnect 
  Interface: Wi-Fi 
  SSID: (your Wi-Fi SSID)

• Rule 2

  Action: Connect  
  No need to input any condition

Then, click Enable VPN On Demand and save the profile.

Note 1: Make sure the profile is selected (showing a checkmark). It will not work if the profile is not selected.

Note 2: The order is important. If you place Rule 2 before Rule 1, Rule 1 will never run because Rule 2 matches any condition. You can change the order by tapping Edit and drag rules into your desired order.

Q: What does the action type "Evaluate Connection" do?

Evaluate Connection is a special action that further assesses the action to take based on the current connection's destination.

If the destination can't be resolved on the current network, one of these actions can be taken.

• Connect If Needed
• Do Not Connect (Ignore)

For example, you can setup the following rule that if some internal website is being requested (not resolvable on the current network), VPN is automatically started.

Action: Connect If Needed
Domain Being Evaluated: companyinternal.com (this will match *.companyinternal.com)

SSTP Questions

Q: Do you offer the same connectivity as the Windows built-in SSTP client?

In most cases we provide the same connectivity as the official client. However in these situations our app does not work for you.

• PEAP authentication is required

SoftEther Questions

Q: If I can connect using the official SoftEther Client, does that mean I can use this app too?

In most cases we provide the same connectivity as the official client. However in these situations our app does not work for you.

• NAT traversal or direct UDP connection is required to connect to the server

Q: What is UDP acceleration and why is iOS 13 / Server 4.30 required?

SoftEther by default connects via direct TCP and data packets are transferred over TCP as well. UDP acceleration enables sending and receiving data packets over UDP. Although it's named acceleration, the speed may or may not be better than TCP, depending heavily on your network condition.

SoftEther has historically implemented two versions of UDP acceleration. The original version encrypts data with RC4 cipher, which has been proved insecure and Apple has ceased its support since iOS 10.

The newer version was introduced in Server 4.30 (Build 9695) and uses ChaCha20-Poly1305 as cipher. Starting iOS 13, Apple has native support to it.

Q: How do I know whether I am using UDP or TCP? Why is UDP not working sometimes?

"UDP" sign will be displayed in the status bar when UDP is used. You can also know it from the connection log.

UDP acceleration has two working mode:

• Direct mode, in which certain ports on the server need to be opened, just as in TCP. This is the most reliable mode.
• NAT traversal mode, where no ports are open but the external IPs of the client and the server are obtained from external servers. Both ends need to be sitting on the public address or behind some specific type of NAT network (called "cone NAT") in order to establish UDP connection. Many cellular network, for example, uses symmetric NAT in IPv4 which does not allow NAT traversal. UDP acceleration will not work in these situations.

IPv6 network does not use NAT and should be naturally supporting UDP acceleration.

Q: After I switch the network, UDP acceleration seems not working and why is that?

This is normal if the UDP acceleration works in NAT traversal mode, because according to the current SoftEther protocol there is no way to renegotiate a new endpoint for an existing session. Therefore the server has no way to know your new address and cannot reach the device after the network switch.

Once you switch back to the original network (provided that your IP address has not changed), the UDP will be probably working again.

You have two options to solve this problem:

• Open the relevant UDP ports on the server side just like you have done for TCP (i.e. Direct mode), or
• Manually reconnect in the new network.

Q: Can I connect to the VPN Azure service?

Yes, you can. Make sure that you use the hostname (xx.vpnazure.net) as the server address. It will not work if you enter an IP address.

Also please note that VPN Azure has two modes:

• Relay mode, which is pure TCP and should work in most occasions but might be slower.
• Direct mode, where data packets are transferred directly to the real server using UDP acceleration.

iOS version, server build and NAT types need to be satisfying the UDP acceleration requirements for direct mode to work.

Q: Can I connect to the VPN Gate service?

Yes. Use these information when you connnect to VPN Gate servers.

• Server: xx.opengw.net (or IP address)
• Hostname: xx.opengw.net (only required if an IP is entered as server)
• Port: TCP port number (UDP is not supported)
• Virtual Hub: vpngate
• Username: vpn
• Password: vpn

CAUTION: VPN Gate servers are provided by various contributors around the world. We do not have any affiliation with them or the project, nor do we ensure connectivity or security in any form.

USE THESE SERVERS AT YOUR OWN RISK!

Other

Q: Sometimes the WiFi icon goes off with the VPN icon for several seconds. What's going on?

This is an indication that VPN is reconnecting. You are not losing your WiFi connection. It's just how iOS responds to VPN reconnecting events.

Q: I want to make sure traffic is blocked during reconnecting events (called "Seamless Tunnel" by OpenVPN). How can I do it?

This feature is already enabled and we do not offer a way to disable it.

However, please note that some system traffic does not go through VPN at all, including push notifications and some DNS requests. This is controlled by iOS.

Q: Can you help with setting up a server?

We don't make server-side products, but we can provide general advice to you. If special assistance is needed, we will evaluate the situation and (in the case that we can help) may give you a quote.

Q: What if I have more questions?

Send an email to support@domosekai.com and we will look into it. If it's a connection issue, please set log level to "debug" and send the connection log along with your mail.