I need to help with my ftp client application. I successfuly connect to server with usename and password and send PASV message. I recived IP and port, but i do not know what to do next. I know that I must connect to IP and port, but I do not know how.
Can somebody give me example of code how to connect and recive message from server?
You already have the code which successfully connected to port 21 on the server, the same code will also work to connect to the IP address and port number that was returned in the PASV response.
BUT
You do not want to make this second connection until it is time to transfer some data. The first connection you established is for commands and responses to commands. The connection you make to the port returned by PASV is for the transfer of data following a command that actually transfers a file, for example RETR or LIST.
Related
I'm trying to create a Camel/Netty TCP client that works as follows:
connect to remoteserver:1234
send a handshake message (pretend it's the string "handshake")
leave this connection open
wait/listen for TCP messages from the server and reply to them
Here's a simple hello-world server.
from("netty:tcp://localhost:8001?textline=true&sync=true") //
.process((exchange) -> {
String msgReceived = exchange.getIn().getBody(String.class);
exchange.getOut().setBody("hello " + msgReceived);
});
I can open a command line TCP connection to this, type in text, and receive my hello-world reply.
Now how do I structure an analogous client that likewise just waits for messages and replies?
When you say "wait/listen for TCP messages from the server and reply to them" you are reversing the roles, now the client acts like a server and the server like a client.
What you could do is set up an incoming route in the client listening on a given port and use the initial handshake message to the server to communicate the client's IP and port.
I created a new VM for SQL Server and trying to setup the dbmail. The smtp server settings are all valid but I can't send emails out. I keep on getting following error:
The mail could not be sent to the recipients because of the mail server failure.
(Sending Mail using Account 1 (2016-07-20T09:19:34).
Exception Message: Could not connect to mail server. (A connection attempt failed because the connected party did not properly respond after a period of time, or established connection failed because connected host has failed to respond 159.122.224.196:587).
)
I tried doing a telnet check on the IP and port no. from my my local machine and SQL Server VM. While the local machine just works fine, the SQL Server VM can't connect to the port.
I also tried to open a port 587 using the link http://michaelsync.net/2015/09/28/where-is-the-endpoint-setting-for-vm-in-new-azure-portal but even after allowing a port 587, I still can't send emails. Any help will be much appreciated.
NOTE: The IP address 159.122.224.196 belongs to sendgrid.
What E-mail (SMTP) server are you using?
Make sure that you're configuring connectivity to it correctly and that the E-mail server is
I'm implementing my own TCP server. So far I can make a connection, that works fine, I can connect to any client. However when I want to send or receive messages from the client it goes wrong. The following is a snippet of the last part of my server, where I want to send the message WeLcOmE to my client (I'm using C programming language & Linux as the OS):
// Accept a connection request
int clientAddress = sizeof(client_address);
int new_socket = accept(door_socket, (struct sockaddr *) &client_address,
&clientAddress);
if (new_socket < 0)
perror("ERROR on accept");
// Receive data from socket, send data to socket
char buff[8] = "WeLcOmE";
send(new_socket, buff, sizeof(buff), 0);
// Close socket
close(new_socket);
close(door_socket);
return 0;
Running my server with a Filezilla Client this is what I get:
Status: Resolving address of ubuntu
Status: Connecting to 127.0.1.1:3471...
Status: Connection established, waiting for welcome message...
Response: WeLcOmE
Error: Could not connect to server
Status: Waiting to retry...
Status: Resolving address of ubuntu
Status: Connecting to 127.0.1.1:3471...
Status: Connection attempt failed with "ECONNREFUSED - Connection
refused by server".
Error: Could not connect to server
Running my server with the ftp Linux built-in client I get:
ftp> WeLcOmE421 service not available remote server has closed connection
I don't understand why is this happening. Any help is appreciated.
As you have yourself stated, you have implemented a "TCP" server. All the server does is that it sends the "WeLcOmE" string to any TCP client that connects to the server.
If you connect with an FTP client to the server, the client gets the "WeLcOmE" string, and as that does not conform to the FTP protocol specification, the client errors.
The same would happen, if you connect with any other client that uses a specific protocol, e.g. a web browser [HTTP], a terminal client [SSH or Telnet], etc.
Now the question is, what you are trying to achieve:
Either you want to implement an FTP server. For that you need to read the FTP specification and implement your server according to it. That's an immense task and in general you do not want to do that. You better take an existing implementation. Either an FTP server library and build your custom FTP server on it. Or take a complete open source FTP server and customize it to your needs.
Or you just play with your toy TCP server and you want to test it. For that use any TCP client that can work in "raw" mode by reading from the socket and just displaying what it gets, without trying to interpret the data in any way. You can use PuTTY in a "raw" connection mode. See section Making raw TCP connections in PuTTY documentation.
I am trying to write a TCP proxy in c. The server only works with non-ephemeral ports. The proxy is trying to mount a file-system. So when I call the mount command by-passing the proxy it chooses an appropriate port and it connects. But when I try to connect via the proxy an appropriate port is selected for the connection between the client and the proxy, but the proxy uses an ephemeral port when it connects to the server.
I have read that it is not wise to specify a port, so I am looking to define a range of ports for it to choose from. Is this possible?
Any advice and help is appreciated. Thanks.
I figured it out. I needed to bind to a reserved port prior to running the connect to the server.
use bindresvport(3) with the server socket.
Firewall is turned off but still it is not able to execute put commend on ftp
ftp>cd /web
250 CWM command successful
ftp>binary
200 Type set to I
ftp>put C:\sample.xml
200 PORT command successful
425 Unable to build data connection: No route to host
Your script works in active mode, e.g. the client gives the server a client side ip and port using the PORT command and the server tries to connect to it. Because the server replies, that it has no route to your host my guess is, that
you are in an internal network, e.g. using a private IP which is not directly accessible from the internet. This IP is used in the PORT command.
the server is on the internet
from the internet the server of course can not connect into a private network, thus you get this error message
Fix: use passive mode (e.g. you should see a PASV not a PORT command)
Windows ftp.exe operates in passive mode and your FTP server may need active FTP transfers.
Test your commands on a different FTP server to see if it works elsewhere.