mTCP | Unofficial fork of https : //www.brutman.com/mTCP | Telnet library

The problem when the 2 containers not able to talk to each other is due to the fact that they are not in the same docker network. Here are what you have to do:

• List all the available networks: docker network ls
• Find out which network the apache container is running in

There is a similar issue raised and answered here

... you are holding the socket object in a class-scoped variable. So, if somehow the socket gets disconnected while the ReadCallback is executing and you reconnect it (thereby changing the socket object) - now they don't match, you are trying to complete the Async request using the new object when the old one is the one actually completing.

In your case it is the variable cState. On Connect method, if you just declare a new instance of cState locally which holds the socket then the error may stops occuring.

There are two possible answers: how to get the MSS (maximum segment size) of a TCP connection and how to parse the TCP header.

If all you want to know is what the MSS of the connection is, then you can use the getsockopt function on an open socket. Pass it the file descriptor, IPPROTO_TCP as the level, TCP_INFO as the option, the address of a struct tcp_info (from tcp.h) that will hold the output, and sizeof (struct tcp_info). The kernel will fill in the fields of struct tcp_info and you can get the MSS from tcpi_snd_mss or tcpi_rcv_mss.

If you actually want to parse the TCP header itself, then you have to understand the layout of the header. The struct tcphdr you're using doesn't include the options, which come after the fields in struct tcphdr. Each option field is a single byte identifying the option kind, optionally followed by a second byte specifying the size of the option (including the kind and size bytes), followed by additional data.

There may not be any options at all. You have to start by looking at the data offset field of the TCP header (doff). It's in 32-bit words. The size of the standard header, defined by struct tcphdr, is 20 bytes, so options can only be present if doff is greater than 5 (times 4 bytes = 20 bytes).

Assuming there are options, you can read them like this. Note that option kind for MSS is 2 and that option kind 0 signifies the end of the options list, but only if the end of the options list doesn't already coincide with the start of the data as per doff. Option kinds 0 and 1 (no-op) are a single byte. The other option kinds have a size byte that follows the kind and specifies the size of the options field (including the kind and size fields).