Return code 00000461 for TCP/IP

There is a channel failure, and you receive the following: CSQX208E TRPTYPE=TCP RC=00000461, or CSQX208E TRPTYPE=TCP RC=00000461 reason=76650446.

Cause

• An unorderly connection termination, such as a rebooting the client box, can cause a reset.
• An application requests a connect to a port and IP address on which no server is listening.
• An application closes a socket with data still in the application receive buffer. The connection is reset to allow the remote partner to know that the data was not delivered.
• Any data that arrives for a connection that has been closed can cause a reset.
• An application closes a socket and sets the linger socket option to zero. This notifies TCP/IP that the connection should not linger.Note: IBM MQ does not code the linger time = 0, therefore IBM MQ itself does not cause a reset.
• A TCP segment that is not valid arrives for a connection. For example, a bad acknowledge or sequence number can cause a reset.
• The connect request times out. TCP stops trying to connect to a particular port and IP address and reset the connection.
• A firewall can reset connections if the packet does not adhere to the firewall rules and policies. For example, a source or destination port, or IP address does not match the firewall rule or policy.
• The retransmit timer expires. TCP stops trying to retransmit a packet and reset the connection.
• A bad hardware device can cause resets.

We need to be aware that the effect of our configuration at higher levels, for example, the channel initiator dispatching priority being too low, could exhibit itself as a reset. Therefore, we should also consider the effect of our configuration when trying to determine why a reset is happening.

Diagnosing the problem

Use TCP/IP packet traces to determine why the reset occurred.

See z/OS UNIX reason codes for the last two bytes of the reason code found in the CSQX208E error message.