This troubleshooting guide addresses the following conditions:

1. An Aspera Scp Client or web client cannot connect to the server, and receives the error "Timeout establishing connection"
2. The Aspera Scp Client or web client seems to connect to the server, but the transfer progress reads 0% and eventually the client receives the error "Data transfer timeout". In this case, the file(s) to be transferred may appear at the destination, but they are 0 bytes in size

The first case is due to blocked TCP connectivity. The Aspera client is trying to contact the server on the designated TCP port (by default 22, but often configured to be 33001). This is due to either the client side firewall preventing outbound TCP access, or a misconfiguration of the server side firewall not allowing inbound TCP traffic to the Aspera server.

Here are the suggested troubleshooting steps for case (1):
 

First make sure that the server is listening to the TCP port. By default, the Aspera server uses the built-in SSHD server on Unix and Mac computers, and installs an SSHD service on Windows. On all platforms, the default TCP port is 22.

• On the server computer, open a command line terminal and try to connect to the local port 22:
  > telnet localhost 22
  This should print an OpenSSH welcome message, and typing Enter again will exit back to the command prompt.
• If the error received is "Connection refused", the SSHD server must not be running, or may not run on the port we expect it to. Check the server configuration file /etc/ssh/sshd_config or on Windows Program Files\Aspera\FASP\etc\sshd_config, and make sure the Port directive is set to the desired TCP port. Restart the SSHD server after making changes to this file.
• If the error received is "Timeout", there must be a local firewall or protection software running on the Aspera computer preventing the SSHD server from running. Identify and disable the local firewall services temporarily, to see if that is causing the problem.

Try to connect to the server's TCP port

• On the client computer, open a command line terminal and try to connect to the server on port 22 (or the configured TCP port, if other than 22)
  > telnet server-ip-address 22
  Replace server-ip-address with the IP address of the Aspera server.
• If the error received is "Connection refused", the Aspera server must not be running the SSHD service. See the Server procedure above.
• If the error received is "Timeout", the problem is the local, client side firewall, which is likely dissallowing outbound TCP traffic. You must make sure that the client side firewall allows outbound TCP traffic on port 22.

The second case is due to blocked UDP connectivity. The control connection over TCP is established, but the data connection, using UDP, cannot be established and thus the file contents cannot be transferred.

Here are the suggested troubleshooting steps for case (2):

• Make sure that the server side firewall allows (or forwards) UDP traffic on port 33001 (or a range of UDP ports for Windows server, for example 33001-33010) to the Aspera computer.
• Make sure that the client side firewall allows outbound UDP traffic.
• If both firewalls seem correctly configured, but the UDP traffic sent by the Aspera client cannot reach the Aspera server, use our UDP tool to test connectivity:
• Download the UDP receiver tool on the Aspera server computer. Choose the binary for your server Operating System.
• Download the UDP sender tool on the Aspera client computer. Choose the binary for your client Operating System.
• Run the UDP receiver tool on the server, from a command line terminal:
  > aspera-udp-rcv 33001
• Run the UDP sender tool on the client, from a command line terminal:
  > aspera-udp-snd server-ip-address 33001 Replace server-ip-address with the IP address of the Aspera server.
• If the aspera-udp-rcv program doesn't print out any information regarding received traffic, it means that no UDP traffic sent by the client reaches the server. Go over steps 1 and 2, and identify the problems in firewall configuration until you see the aspera-udp-rcv program printing out information regarding received UDP traffic.