SOLCLIENT_STATS_TX_SOCKET_FULL is a count of the number of times the API attempted to write to the socket and was unable to write all the data. This forces the API to buffer internally the rest of the message, at some point solClient_session_sendMsg() will block because the API buffer is full too. It is typically an indication of how slow your network is, but if it is exactly 100 for 100 messages I’d go out on a limb and guess you were sending very large messages, over 1MB each, possibly many MB.
It’s not really a problem, if you are finding that your transmission rate is considerably lower than your available bandwidth you might tune up the socket buffer size but it is quite large already and this seldom gains much.
The number of messages a client can receive on a topic is completely application dependent. There is no way for the broker to signal ‘end of messages on topic’ as there is theoretically no end to the messages. If you wish to communicate this from publisher to client you must do this inside the application/protocol you design, perhaps by adding a special ‘end-of-messagst’ message that the client will recognize.