So i did this tutorial exactly the same and im getting the Windows socket error: 10049. This is the tutiroal: https://docwiki.embarcadero.com/CodeExamples/Sydney/en/Chat_Room_Socket_(Delphi)
What is the problem here?
The problem you are facing here is that you are stil using port 0 (default values for both TClientSocket and TServerSocket components).
You should change the port number of both client and server component to be something else than 0. I recommend using ports greater than 1024 in order to avoid using reserved ports.
In fact you might want to consider checking IANA Service Name and Transport Protocol Port Number Registry to make sure the port you will be using isn't registered to another application or service.
PS: Embarcadero should have provided information about the need to change port number used in their example.
Related
I'm trying to establish a connection using sockets between 2 PC's on the same LAN using the Eiffel Programming Language. I'm trying to run the examples that are by default on the installation directory of Eiffel Studio. However right now I'm trying to make it on the same machine by addressing to localhost (127.0.0.1).
It works perfectly on Linux (Ubuntu 15.10) but on windows 7 I'm getting an exception when I try to run the client program. The code of the exception is 24 Unable to establish connection. The server program runs just fine and I already got a connection between a client on linux and a server on windows. I didn't find a solution to this exception on the documentation nor on other sites. Here is a screencap:
Screencap of the debugger
Here is a link to the doc:
https://www.eiffel.org/doc/solutions/Two%20Machines
Thank you in advance.
The issue might be caused by the fact that some ports are used and others are reserved by the system. In particular the port range 0-1023 is designated for use by common system and network services. Ports beyond this range can also be registered (e.g., Service Name and Transport Protocol Port Number Registry or List of TCP and UDP port numbers). System security settings could also prevent applications from using specific port numbers.
The solution is to look for and to use port numbers that are available for user applications. Ports currently used on Windows can be found with netstat -an, what can be used is related to TCP/IP and firewall settings. The simplest approach is to try using some other port numbers, e.g. in the range 1024-49151.
I need to write my first socket program involving TCP connections. In the program I have created there is a client and server, both of which are the machine I am coding on.However,it requires that I pass the port number as a command line argument. How do I accomplish this?
The answer is simple : Make sure your server and your client agree on the port to use. As long as the port is available and can be used, set up the connected so that the client and server use that same port.
Here's a link that explain the different ranges available for TCP and UDP ports.
As an exemple, the port 3074 is used by microsoft for its Xbox live service. Making an application using this port might interfere with the service.
The port used will be defined either in a configuration file or hard-coded in the source code of both the server and the client. You should easily be able to find it with a quick look at the code or the directory which contains the application.
I connect to a web server supported by an embedded system with Internet Explorer 9. Windows 7 is on the client side.
The web page have many tabs and I browse across until the problem occurs. It takes about one minute to happen.
The embedded system freezes so it not possible to browse and it does not respond to ping. After a moment the embedded system will recover because it is designed to reboot. I joined a Wireshark trace in which you can see 92 connections (use the filter "tcp.stream eq 0" with values [0,91]) and you will see. I have the source code so I know that the embedded system does not support more than 37 simultaneous connections. Is the cause an exhaustion of the resources?
But I have a more basic question and I really more appreciate an answer to it. The web server is at 172.21.1.12 port 80 and the client is at
172.21.9.70 and variable port numbers (see the trace). Because the IP and port on the server side do not change, how many sockets are in use on the server side? The question is important because the more sockets are opened, the more probably there is an exhaustion of the resources.
If the answer is only 1 socket then I must conclude there is no lack of resources because it can support 37.
I also suggest you use the filter ip.addr == 172.21.1.12 in Wireshark.
I thought I could upload the wireshark file. I dont know how to share it with you. Help please?
Dropbox?
Under the caveat that you haven't specified your embedded system, most TCP stacks will create a new socket for each new connection, and the mapping from socket to connection is 1-1.
When a packet arrives to the network stack, it has to associate that packet to the right socket. Usually, this is accomplished by employing a map from the TCP 4-tuple to the socket, where the 4-tuple consists of [local-ip, local-port, remote-ip, remote-port].
A server makes its service available by listening on a fixed local port that is known to clients wanting to use the service. As you understand, this is usually port 80 for a web server, and the software interface for most TCP implementations dedicate a socket for the purpose of allowing the API to perform operations on the network parameters for this service. However, the socket is not fully connected (the last two parts of the 4-tuple are set to a special "not specified" value, usually all bits 0). When a new connection is accepted, a new socket is created where the 4-tuple consists of the local information of the listening socket and the remote information taken from the source address and port of the SYN packet that initiated the TCP connection.
The limit on the number of connections a server can support is based on how the operating system is configured (you say yours limits it to 37). Using the 4-tuple, a single service (that is a fixed local-ip and local-port) will have an absolute limit of (2ADDR_BITS - RESERVED_ADDRS) × (216 - RESERVED_PORTS). For IPv4, the number of bits is 32, while for IPv6, the number of bits is 128.
When creating a connection, the client will specify the destination address and port (which fills out the remote information for the 4-tuple), but usually leave the source information unspecified. The TCP stack will choose an appropriate source address based on routing, and select an available source port (which will become the local information to complete the 4-tuple). In theory, any source port that is not being used by the selected local interface to communicate to the same remote service can be used as the local port. Most stacks will dedicate a set of the higher numbered ports for this purpose (referred to as the ephemeral port range).
I have 2 sip clients on the same computer.
Both of them is registering to a server that is running on port 5060.
For the first client the UDP is on port 5060 and for the other is 5061. When I come from one client to another, after the ringing part i receive the error:
only one usage of each socket address is normally permited.
Got any ideas why I got this error?
Your server and client are both trying to use port 5060, hence the error message. Change the first client to use 5062 or something else.
Also, 5061 is normally used for secured SIP (normal listening port + 1 in the proxy/server). Do not use it for the second client.
It means you're clients are both trying to claim the same socket for the communication channel, or the server is trying to reclaim the socket given to client A, to reuse it for client B.
The software handeling the socket, should be smart enough to rely on the OS to assign port numbers instead of hardcoding the port numbers in the code, this is a 100% guarantee for socket issues.
Just curious. When developing with Casini development server, one has an infinite number of ports. But, the production servers seem to give a particular importance to port 80.
Has that to do with a technical requirement, a convention, or both? I've checked the web but haven't been able to find a clear response so far.
Thanks for helping.
Many services have specifically-assigned ports This allows users to type, for example http://stackoverflow.com and get the website for SO, without needing to enter a port as well. This isn't a technical requirement; however, using a different port requires the user to know an extra piece of information, which must be entered into the URL every time.
When you connect to a server via TCP/IP you specify particular port you connect to. You do not connect to a server and hope that server guesses which port you would like to talk to.
So in most cases you tell browser to use protocol http, say "http://example.com/" then browser uses default port number assigned to that protocol (http) to connect to server "example.com". In this case port is 80. If for example you specify "https://example.com/" then browser looks for default port for https and then connects to port 443 instead.
So if you do not want to tell to every of your users to specify some non-default port for your service (say "http://example.com:60765/") you better use default one.
BTW there is a way to get port number your service listens to by it's protocol name (by asking a service's host's daemon at port 0) but this method seems to be rarely used (if at all).
See also other answers: default protocol numbers are assigned by IANA
It's a convention: you can use whatever port you feel like. You can look at the evolution of RFCs to see when the convention was official (http://www.faqs.org/rfcs/rfc1700.html)
You can see in the RFC 1060 (http://www.faqs.org/rfcs/rfc1060.html ) that it's the ISO Internet Protocol :)
In a production environment your web server is embedded in a server infrastructure (firewalls, proxies) protecting you against attacks from the internet. In such an environment port 80 is normally open for HTTP traffic. If you use this port there is no need to configure your server infrastructure.