TCP proxy

A TCP proxy is software that accepts connections and "forwards" them to the desired resource for additional data security. The point is not in the connection's safety but in the enhanced guarantee that the traffic will reach the recipient entirely in its original form without errors and in the correct order.

Using the same UPD and TCP files are transferred as one significant stream of bytes. The order of the transmitted information can not only get mixed up but even get partially lost. When using TCP proxy, the stream of bytes is divided into several segments. Each segment is sent separately, and then it is already connected at the "end" as a whole.

The guarantor of reliable delivery is the response from the receiving side. After sending each segment, carrying a new piece of information does not begin without acknowledging receipt of the previous segment. The sender sets a timer waiting for the response. If no acknowledgement is received after a specific time and part of the information is lost before it reaches the recipient, the segment is automatically resent.

Operation in sliding window mode is possible. It is most effective when you need to transfer a massive amount of information. In this case, the user sends several segments one after the other and then receives a cumulative confirmation that all data have been received. Severe delays may occur when using the segment-response method. It is preferable to use a "sliding window" mode for a higher data rate in operation.

TCP uses a connection established before data is sent; once the connection is established, it works both ways: each of the connected agents can start sending data. Byte numbering is used to ensure that messages come in the correct order. The TCP protocol has a built-in mechanism to protect against duplication of segments that have already been sent.