While Download Works But Post Request Not (Chilkat) - vb.net

Question

I am facing a very wired issue, and passed so many hours to find the issue but without any luck :(
i have setup a web server on my mobile (android)..
and trying to use that using my vb application
where i simple call Download method on the very sample url (same ip/port), it works and save the response body as downloaded file.
but when i try to send post command it is not working, it gives error "Connection rejected"
here is the code to download:
objDHTTP.Download("http://192.168.1.101:8000/fileAdmin.php", strAppDir & "\wtf-response.txt")
here is the code when i tried to use same url and port for post request:
objDRequest.Path = "/fileAdmin.php"
objDRequest.AddParam("fileAction", "Upload")
objDRequest.AddParam("fileName", "DB.sql")
objDRequest.AddFileForUpload("adminFile", strAppDir & "\c.dll")
objDResponse = objDHTTP.SynchronousRequest(strServerIP, 8000, False, objDRequest)
but it does not works and throws above error
here is the success response (for download method):
<ChilkatLog>
<Download>
<DllDate>Dec 21 2018</DllDate>
<ChilkatVersion>9.5.0.76</ChilkatVersion>
<Architecture>Little Endian; 32-bit</Architecture>
<Language>.NET 4.0</Language>
<VerboseLogging>0</VerboseLogging>
<url>http://192.168.1.101:8000/fileAdmin.php</url>
<toLocalPath>G:\wtf-sucess.txt</toLocalPath>
<currentWorkingDir>G:\</currentWorkingDir>
<a_httpDownload>
<httpDownloadFile>
<localFilePath>G:\wtf-sucess.txt</localFilePath>
<localFileAlreadyExists>1</localFileAlreadyExists>
<quickHttpRequest>
<httpVerb>GET</httpVerb>
<url>http://192.168.1.101:8000/fileAdmin.php</url>
<openHttpConnection>
<info>Opening connection directly to HTTP server.</info>
<httpHostname>192.168.1.101</httpHostname>
<httpPort>8000</httpPort>
<tls>False</tls>
<info>HTTP connection succeeded.</info>
</openHttpConnection>
<buildQuickRequest>
<genStartLine>
<startLine>GET /fileAdmin.php HTTP/1.1</startLine>
</genStartLine>
<addCookies>
<info>Not auto-adding cookies.</info>
<sendCookies>1</sendCookies>
<cookieDir></cookieDir>
</addCookies>
</buildQuickRequest>
<sendRequestHeader>
<sendHeaderElapsedMs>0</sendHeaderElapsedMs>
</sendRequestHeader>
<statusCode>200</statusCode>
<statusText>OK</statusText>
<checkCloseConnection>
<info>Response includes connection:close header (or proxy-connection:close header)</info>
</checkCloseConnection>
</quickHttpRequest>
<outputLocalFileSize>26</outputLocalFileSize>
<numOutputBytesWritten>26</numOutputBytesWritten>
</httpDownloadFile>
</a_httpDownload>
<totalElapsedMs>47</totalElapsedMs>
<ContentLength>0</ContentLength>
<info>Success.</info>
</Download>
</ChilkatLog>
And here is the error/fail response (for post request):
<ChilkatLog>
<SynchronousRequest>
<DllDate>Dec 21 2018</DllDate>
<ChilkatVersion>9.5.0.76</ChilkatVersion>
<Architecture>Little Endian; 32-bit</Architecture>
<Language>.NET 4.0</Language>
<VerboseLogging>0</VerboseLogging>
<domain>191.168.1.101</domain>
<port>8000</port>
<ssl>0</ssl>
<httpRequest>
<httpVersion>1.1</httpVersion>
<verb>POST</verb>
<path>/fileAdmin.php</path>
<contentType>multipart/form-data</contentType>
<charset>windows-1252</charset>
<sendCharset>0</sendCharset>
<mimeHeader></mimeHeader>
<requestParams>
<requestItem>
<name>fileAction</name>
<value>Upload</value>
</requestItem>
<requestItem>
<name>fileName</name>
<value>DB.sql</value>
</requestItem>
<requestItem>
<name>adminFile</name>
<fileOnDisk>G:\c.dll</fileOnDisk>
<numValueBytes>8697</numValueBytes>
</requestItem>
</requestParams>
</httpRequest>
<fullRequest>
<a_synchronousRequest>
<generateRequestHeader>
<httpRequestGenStartLine>
<genStartLine>
<startLine>POST /fileAdmin.php HTTP/1.1</startLine>
</genStartLine>
</httpRequestGenStartLine>
<addCookies>
<info>Not auto-adding cookies.</info>
<sendCookies>1</sendCookies>
<cookieDir></cookieDir>
</addCookies>
<genMultipartFormData>
<requestParam>
<name>fileAction</name>
</requestParam>
<requestParam>
<name>fileName</name>
</requestParam>
<requestParam>
<name>adminFile</name>
<filename>G:\c.dll</filename>
</requestParam>
</genMultipartFormData>
</generateRequestHeader>
<fullHttpRequest>
<domain>191.168.1.101</domain>
<port>8000</port>
<ssl>0</ssl>
<openHttpConnection>
<info>Opening connection directly to HTTP server.</info>
<httpHostname>191.168.1.101</httpHostname>
<httpPort>8000</httpPort>
<tls>False</tls>
<socket2Connect>
<connect2>
<connectSocket>
<connect_ipv6_or_ipv4>
<info>Connection attempt failed.</info>
<maxWaitTimeMs>10000</maxWaitTimeMs>
<totalMsWaitedSoFar>2100</totalMsWaitedSoFar>
</connect_ipv6_or_ipv4>
<connect_ipv6_or_ipv4>
<info>Connection attempt failed.</info>
<maxWaitTimeMs>10000</maxWaitTimeMs>
<totalMsWaitedSoFar>2150</totalMsWaitedSoFar>
</connect_ipv6_or_ipv4>
</connectSocket>
<ConnectFailReason>Connection rejected</ConnectFailReason>
<error>A few possible causes for a connection being rejected are:</error>
<error>- A firewall (software or hardware), such as Windows Firewall, is blocking the connection .</error>
<error>- Nothing is listening at the remote host:port</error>
</connect2>
</socket2Connect>
</openHttpConnection>
</fullHttpRequest>
<success>0</success>
</a_synchronousRequest>
<success>0</success>
</fullRequest>
<totalTime>Elapsed time: 4390 millisec</totalTime>
<error>Failed.</error>
</SynchronousRequest>
</ChilkatLog>
can any one tell me what could be the reason for this?
thanks in advance
best regards

Answer 1

The likely reasons are present in the LastErrorText:
<ConnectFailReason>Connection rejected</ConnectFailReason>
<error>A few possible causes for a connection being rejected are:</error>
<error>- A firewall (software or hardware), such as Windows Firewall, is blocking the connection .</error>
<error>- Nothing is listening at the remote host:port</error>
My guess is that the Windows Firewall is blocking the outbound POST.
This example shows the errors one would get for various TCP socket connection problems: https://www.example-code.com/vbnet/socket_connect_fail.asp