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The conn_id_tcp argument represents the TCP connection handle — not the socket handle. The following code may be used to get the TCP connection handle and configure TCP connection parameters (see also NetSock_GetConnTransportID):
NetTCP_ConnCfgReTxMaxTimeout() is called by application function(s) and must not be called with the global network lock already acquired. It must block all other network protocol tasks by pending on and acquiring the global network lock (see “net.h Note #3”). This is required since an application's network protocol suite API function access is asynchronous to other network protocol tasks.