Re: [fpc-pascal] SOLVED fpSelect fails with UDP sockets?

[Klaus Hartnegg]

It works with
  rc := fpSelect (sock+1,@FDS,nil,nil,5000);
I did not understand the description of the first argument in the docs, 
so I used the value from the sample, this was not a good idea.


For reference here is the source that works:

Uses
  UnixType, BaseUnix, Sockets;

procedure abort (reason:string);
begin
  writeln (reason);
  halt;
end;

var
  sock: cint;
  ladr : SockAddr;
  radr : SockAddr;
  adrlen: tSockLen;
  msg : string[255];
  FDS : Tfdset;
  rc  : cint;

begin
  sock := fpSocket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
  if sock = -1 then
     abort ('Error from fpSocket');

  ladr.sin_family      := AF_INET;
  ladr.sin_addr.s_addr := INADDR_ANY;
  ladr.sin_port        := htons(2000);
  rc := fpBind (sock, @ladr, sizeof(ladr));
  if rc <> 0 then
     abort ('Error from fpBind');

  adrlen := sizeof(radr);

  Fpfd_zero (FDS);
  FpFd_set (sock,FDS);
  rc := fpSelect (sock+1,@FDS,nil,nil,5000);
  writeln (rc);
  if rc = -1 then
     abort ('Error from fpSelect');
  if rc = 0 then
     abort ('timeout');

  rc := fpRecvFrom (sock, @msg[1], 255, 0 {flags}, @radr, @adrlen);
  if rc = -1 then
     abort ('Error from FpRecv');

  if rc > 255 then
     rc := 255;
  msg[0] := chr(rc);
  writeln (msg);
end.



And this is the sender:

Uses
  UnixType, BaseUnix, Sockets;

procedure abort (reason:string);
begin
  writeln (reason);
  halt;
end;

var
  sock: cint;
  sadr: {TInet}SockAddr;
  dadr: {TInet}SockAddr;
  adrlen: tSockLen;
  msg : string;
  rc  : cint;

begin
  sock := fpSocket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
  if sock = -1 then
     abort ('Error from fpSocket');

  sadr.sin_family      := AF_INET;
  sadr.sin_addr.s_addr := INADDR_ANY;
  sadr.sin_port        := 0; { auto-select }
  rc := fpBind (sock, @sadr, sizeof(sadr));
  if rc <> 0 then
     abort ('Error from fpBind');

  dadr.sin_family := AF_INET;
  dadr.sin_addr.s_bytes[1] := 127;
  dadr.sin_addr.s_bytes[2] := 0;
  dadr.sin_addr.s_bytes[2] := 0;
  dadr.sin_addr.s_bytes[2] := 1;
  dadr.sin_port   := htons(2000);
  adrlen := sizeof(dadr);

  msg := 'hello, world!';

  rc := fpSendTo (sock, @msg[1], length(msg), 0 {flags}, @dadr, adrlen);
  if rc = length(msg) then
     writeln ('ok');
end.
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