Beginning with Chilkat v9.4.0, two new TCP socket performance properties, SoSndBuf and SoRcvBuf, will be added to each of the following Chilkat components/libs: FTP2, HTTP, SFTP, SSH, SshTunnel, IMAP, and MailMan (POP3/SMTP).

These properties allow for the underlying socket’s send and receive buffer sizes to be set. These are socket options associated with the setsockopt system call (see http://linux.die.net/man/2/setsockopt ) using the SO_SNDBUF and SO_RCVBUF options.

It is recommended that these socket options remain unchanged unless performance seems slow. If uploads seems slow, then set the SoSndBuf to a larger buffer size. It is recommended to use buffer sizes that are a multiple of 4096. The default buffer size varies from system to system. To get the value, examine the LastErrorText property after calling any Chilkat method that establishes a TCP connection. The socket’s send and receive buffer sizes will be reported.

Likewise, if downloads seem slow, set the SoRcvBuf to a larger value.

For more information about TCP performance, see these web pages:

http://onlamp.com/pub/a/onlamp/2005/11/17/tcp_tuning.html

http://smallvoid.com/article/winnt-winsock-buffer.html

http://www.ibm.com/developerworks/linux/library/l-hisock/index.html