TCP / IP框架，散布的消息

Question

I'm just diving into some TCP/IP sockets programming in .NET, and I'm beginning to understand how to use message framing to distinguish "messages" in the TCP/IP data stream, for example using message start and end delimiters.

However, I'm not able to wrap my head around what happens if message bytes are sent interspersed with one another. Consider the following scenario (I'm not even sure if this scenario makes sense, so please let me know if I'm misunderstand something):

Rule 1: A web service must send a TCP/IP message to a particular client when it receives a new HTTP request.

Rule 2: The message that the web service will send via via TCP/IP to the client will be ASCII-formatted, and the message will be "+MESSAGE_TEXT|", with a plus sign as the message start delimiter and a pipe symbol as the message end delimiter.

Rule 3: In the client, each byte will be checked as it is received, and when it receives a message 'start' delimiter, it will begin populating a new string with the ASCII-encoded message. When a message 'end' delimiter is received, it will know that the message is complete and process it.

Scenario: The web service receives two HTTP requests simultaneously, which causes two messages to be sent via TCP/IP to the client and when the bytes are received and re-assembled they look like this (ASCII-encoded): "+ME+MESSSSAGE_AGESTART|_START|".

I realize that HTTP requests that are actually "simultaneous" are relatively rare, but since each HTTP Request is essentially in its own thread, this is a possibility. Is this a likely scenario? If so, how do you know which bytes go with which message? Or am I simply confused about the whole thing?

Thanks!

Answer 1

The code that sends data to the client must regulate up the data that is sending on the socket.

If you have multiple threads all using the same connection use a lock on the socket stream and keep the lock till the message has been completely sent, this will keep other threads from causing intermixed messages.

The other way to do it is have a dedicated thread reading from a queue of messages and sending them off, then each message gets put on to the queue and they get sent as they get processed.