Delphi DLL

FTP Socket Buffer and Address Options

Demonstrates the SoRcvBuf, SoSndBuf, PreferIpv6, and ClientIpAddress properties.

Background: These are low-level knobs for specific situations. Larger send/receive buffers can improve throughput on high-bandwidth, high-latency links, though the defaults suit the common case. PreferIpv6 only matters when a hostname resolves to both address families, choosing which to try first. ClientIpAddress is normally left unset; set it on a multihomed host to bind the outgoing connection to a particular local interface. Change any of these only with a concrete reason.

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Delphi DLL

var
success: Boolean;
ftp: HCkFtp2;

begin
success := False;

ftp := CkFtp2_Create();

CkFtp2_putHostname(ftp,'ftp.example.com');
CkFtp2_putUsername(ftp,'myFtpLogin');

//  SoRcvBuf and SoSndBuf set the TCP socket receive/send buffer sizes.  The defaults are tuned for
//  the common case; larger values can sometimes help throughput on high-latency links.
CkFtp2_putSoRcvBuf(ftp,4194304);
CkFtp2_putSoSndBuf(ftp,524288);

//  PreferIpv6 (default 0) chooses IPv6 over IPv4 when a hostname resolves to both.
CkFtp2_putPreferIpv6(ftp,False);

//  ClientIpAddress is normally left unset; set it on a multihomed host to bind the outgoing
//  connection to a specific local interface.
CkFtp2_putClientIpAddress(ftp,'192.168.1.50');

//  Normally you would not hard-code the password in source.  You should instead obtain it
//  from an interactive prompt, environment variable, or a secrets vault.
CkFtp2_putPassword(ftp,'myPassword');

success := CkFtp2_Connect(ftp);
if (success = False) then
  begin
    Memo1.Lines.Add(CkFtp2__lastErrorText(ftp));
    Exit;
  end;

Memo1.Lines.Add('Connected with custom socket options.');

success := CkFtp2_Disconnect(ftp);
if (success = False) then
  begin
    Memo1.Lines.Add(CkFtp2__lastErrorText(ftp));
    Exit;
  end;

CkFtp2_Dispose(ftp);