ConnectionReset The connection was reset by the remote peer.
It's fatal. The remote server has sent you a RST packet, which indicates an immediate dropping of the connection, rather than the usual handshake.
This bypasses绕开 the normal half-closed state transition过渡，转变
"Connection reset by peer" is the TCP/IP equivalent of slamming砰地关上；猛力抨击 the phone back on the hook.This can happen if the other side crashes and then comes back up,
This means that a TCP RST was received and the connection is now closed.
This occurs when a packet is sent from your end of the connection but the other end does not recognize the connection;
it will send back a packet with the RST bit set in order to forcibly强制地 close the connection.
This can happen if the other side crashes and then comes back up, or if it calls close() on the socket while there is data from you in transit运输,
and is an indication to you that some of the data that you previously sent may not have been received.
It is up to you whether that is an error;
if the information you were sending was only for the benefit of the remote client then it may not matter that any final data may have been lost.
However you should close the socket and free up any other resources associated with the connection.
基础概念
RST packet
A RST packet is sent either in the middle of the 3-way handshake when the server rejects the connection or is unavailable OR in the middle of data transfer when either the server or client becomes unavailble or rejects further communication without the formal 4-way TCP connection termination process.