TCP Errors, Explained!
Put simply, TCP is a connection-oriented protocol that allows two devices to talk to each other. Due to the connection-oriented nature of the protocol, a connection between the client and server must be established before any data can be exchanged. The connection is established between the client and the server using the three-way handshake.
This post will look at the possible errors that are thrown along with the reason for the error. Let’s drive right into it, shall we?
A connection attempt failed because the connected party did not respond did not properly respond after a period of time
This is one of the common errors occur during the connection establishment phase. This error is thrown when one device is not able to connect to the other device. One example of when this error can be thrown is outlined below:
When a client initiates a connection, it will send a “SYN” message to the server and it will wait for 3 seconds. This timeout is defined in the Windows registry and it is system wide setting and not application specific. If the client does not receive the “SYN, ACK” within 3 seconds, then it will attempt to connect again, by sending one more “SYN” packet. This time, the client will wait for 6 seconds. The default behavior is to double the previous timeout and try again. The client will retry for 2 more times and if it never receives “SYN, ACK” then it will throw the error. The number of retry attempts is defined in the Windows registry and it is a system wide setting and it is not application specific.
No connection could be made because the target machine actively refused it
This error is thrown when the client is attempting to connect to the server that is not listening on any port. One example of when this error can be thrown is outlined below:
When the client initiates a connection, it will send a “SYN” message to the server. If the server responds with an “RST” instead of a “SYN, ACK”, the client will retry for 2 times and then it will throw the error. The number of retry attempts is defined in the Windows registry and it is a system wide setting and it is not application specific.
An established connection was aborted by the software in your host machine
This error thrown after the connection has been established between the devices and you are attempting to either send or receive data. One example of when this error can be thrown is outlined below:
When a device sends a packet, it will wait for the ACK from the other device for a maximum of 3 seconds. This timeout is defined in the Windows registry and it is system wide setting and not application specific. If the device does not receive the ACK within 3 seconds, then it will re attempt sending the packet. This time, the new PC will wait for 6 seconds. The default behavior is to double the previous timeout and try again. The device will retry for 2 times and then it will throw the error.
An existing connection was forcibly closed by the remote host
This will happen when the peer device sends an “RST” packet. This will generally happen when the application running on the peer device crashes or if the application has disposed the socket.