Re: C++ TCP code differences Pi-3 to Pi-4?


What is the value of errno after the failed accept?   When you get the value of errno, you can look it up in errno.h to find the meaning.


On Wed, Sep 9, 2020, 02:49 Larry K8UT <K8UT@...> wrote:
Thanks for the hints and suggestions. On a whim, I loaded a microSD card with the beta Raspberry Pi 64 bit OS and ... it works! Fearing my success was a fluke, I loaded/reloaded microSD cards with production 32 bit versions and beta 64 bit versions, inserting them in 2gb and 8gb Pi-4 hardware. Identical results in all tests: 32 bit platform fails at socket Accept stage; 64 bit succeeds.

Here's the code. Works on 32 bit Pi-3, on 64 bit Pi-4; not on 32 bit Pi-4:
//----- get TCP Packet String from CLIENT console-----------------------
string getTcpPacketString(int localSocket ) {
socklen_t clilen;
struct sockaddr_in cliaddr;
int newsockfd;
signal(SIGCHLD, SIG_IGN);// delete zombie fork processes
// waiting for poll()
int pResult = poll(fds, nfds, timeout);
if ( pResult == -1 ) { error("ERROR on socket poll()\n"); }
if ( pResult == 0 ) { usleep(10000); return ""; } // no client connected during this cycle
    newsockfd = accept(localSocket, (struct sockaddr *) &cliaddr, &clilen);
    if (newsockfd < 0) {
cout << "Error on accept..." << endl;
return "-1";
//error("ERROR on accept");
uint maxPacketSize = 2048;
char packet_data[maxPacketSize];
memcpy(packet_data, "\0", maxPacketSize);
uint received_bytes = read( newsockfd, packet_data, maxPacketSize);
if (received_bytes < 0) { error("ERROR reading from socket"); }
string localString(packet_data);
localString = localString.substr(0, received_bytes); 
// return a substring, else that entire DIM size is returned with trailing random chars
return localString;
} // end getTcpPacketString ------------------------------------------

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