Getting Ip from socket.

This is a discussion on Getting Ip from socket. within the Networking/Device Communication forums, part of the General Programming Boards category; but do i call getpeername before calling inet_ntoa()? because otherwise wouldn't the sockaddr struct be empty? And, if this is ...

  1. #16
    Registered User
    Join Date
    Apr 2004
    Posts
    102
    but do i call getpeername before calling inet_ntoa()? because otherwise wouldn't the sockaddr struct be empty?
    And, if this is the case then how is it possible because getpeername() will not accept a sockaddr_in struct, only sockaddr.
    Basically, i have a socket, nothin else and i need to get the IP adress from it.

  2. #17
    Registered User
    Join Date
    Sep 2004
    Location
    California
    Posts
    3,246
    Why does the direct-connect'ing client have to listen on a different port than the server? They're not on the same machine, so you shouldn't run into a port conflict...
    Well, the question asker said:

    would they have to use another port from the one they were using to connect to the server?
    If a client is currently using port X to connect to the server, then it could not use port X to connect to a client at the same time because that port is already in use. Now the client that is doing the listening could listen on the same port the server was listening on. Maybe I was just a little unclear on what Mr. Boolean was asking

  3. #18
    Registered User
    Join Date
    Sep 2004
    Location
    California
    Posts
    3,246
    how is it possible because getpeername() will not accept a sockaddr_in struct, only sockaddr.
    Just cast the socketaddr_in to a sockaddr structure when you are passing it to getpeername().

  4. #19
    Carnivore ('-'v) Hunter2's Avatar
    Join Date
    May 2002
    Posts
    2,879
    >>because getpeername() will not accept a sockaddr_in struct, only sockaddr.
    No, it takes a SOCKADDR*. Pass (SOCKADDR*)&theSockAddr_In.

    If a client is currently using port X to connect to the server, then it could not use port X to connect to a client at the same time because that port is already in use.
    I don't believe this is correct. You can connect to as many different servers as you want, using the same port (if you don't believe me, try it: Create a listening socket on port 22222, then create 5 sockets, and connect to 127.0.0.1 on port 22222 with each of them (without disconnecting in between). It will succeed.

    The thing to remember here is that:
    1) There is a central server, listening on port X
    2) Each client connects to the central server on port X
    3) Each client may also listen on port X, on their local machine.
    4) Each client may connect to another listening client on port X

    Each client acts as a server of its own, and requests/accepts connections on port X for peer file transfers, but that does not mean that it cannot also maintain a connection to the central server on port X.
    Last edited by Hunter2; 10-16-2004 at 02:10 PM.
    Just Google It. √

    (\ /)
    ( . .)
    c(")(") This is bunny. Copy and paste bunny into your signature to help him gain world domination.

  5. #20
    Registered User
    Join Date
    Sep 2004
    Location
    California
    Posts
    3,246
    I don't believe this is correct. You can connect to as many different servers as you want, using the same port (if you don't believe me, try it: Create a listening socket on port 22222, then create 5 sockets, and connect to 127.0.0.1 on port 22222 with each of them
    I realize this is true, and I never said otherwise. What I said is that a client cannot connect to two different places using the same port. To use your example, lets say the client connects to the server (which is listening on port 22222) via port 10000. The client cannot make another connection to the server using port 10000, it must use a different port. Read what I said again a little more carefully

    If a client is currently using port X to connect to the server, then it could not use port X to connect to a client at the same time because that port is already in use.

  6. #21
    Yes, my avatar is stolen anonytmouse's Avatar
    Join Date
    Dec 2002
    Posts
    2,544
    I think we have clarified that Hunter2 is talking about the destination port while bithub was referring to the source port. No need to hash it out any further (unless you want to, these threads are always entertaining for bystanders).

  7. #22
    Registered User
    Join Date
    Sep 2004
    Location
    California
    Posts
    3,246
    I was simply clarifying my previous posts because Hunter thought I was referring to something that I was not. If hunter understands what I was talking about now, then I am done (unless the thread starter still needs further clarifications).

  8. #23
    Carnivore ('-'v) Hunter2's Avatar
    Join Date
    May 2002
    Posts
    2,879
    >>the client connects to the server (which is listening on port 22222) via port 10000.
    >Hunter2 is talking about the destination port while bithub was referring to the source port.

    Oh, great. So there's more than one kind?

    >>using the same port
    So the distinction here is between "using" a port and "on" a port? Then does the term "port" in bithub's sense simply mean a socket of sorts?
    Just Google It. √

    (\ /)
    ( . .)
    c(")(") This is bunny. Copy and paste bunny into your signature to help him gain world domination.

  9. #24
    Registered User
    Join Date
    Apr 2004
    Posts
    102
    thanks for all the help, i am now successfully getting the clients IP address.

  10. #25
    Yes, my avatar is stolen anonytmouse's Avatar
    Join Date
    Dec 2002
    Posts
    2,544
    >> Oh, great. So there's more than one kind? <<

    Each connected socket has a source ip address and a source port as well as a destination ip address and destination port. These four bits of information are used by the socket provider to associate a packet with a connection.

    Typically, the socket provider automatically selects the source ip address (most computers only have one ip address) and source port when you call connect(). This means that the source port and ip address is usually totally transparent to your program. You can retrieve the source ip address and port after a socket is connected using getsockname().

    You can also specify the source port and ip address of a socket before you call connect() with a call to bind(). However, due to the possibility of conflicts this is strongly discouraged:
    Quote Originally Posted by MSDN
    Binding to a specific port number other than port 0(ed's note: port 0 means use automatic selection) is discouraged for client applications, since there is a danger of conflicting with another socket already using that port number.
    You can view source and destination information for current connections using the console command netstat -n. For example, this printout shows three connections from my computer to a website (actually a random ip address):
    Code:
      Proto  Local Address          Foreign Address        State
      TCP    192.168.0.55:2824        99.143.76.204:80        ESTABLISHED
      TCP    192.168.0.55:2825        99.143.76.204:80        ESTABLISHED
      TCP    192.168.0.55:2826        99.143.76.204:80        ESTABLISHED
    Note the different source ports. All other things being equal (source address, destination address, destination port), the socket provider uses the source port to differentiate between these connections.

    When one refers to a port, in relation to sockets, they are usually, but not always, referring to the destination port. Hence the confusion.

  11. #26
    Carnivore ('-'v) Hunter2's Avatar
    Join Date
    May 2002
    Posts
    2,879
    Ok, thanks. I get it now
    Just Google It. √

    (\ /)
    ( . .)
    c(")(") This is bunny. Copy and paste bunny into your signature to help him gain world domination.

  12. #27
    Registered User
    Join Date
    Apr 2004
    Posts
    102
    sorry about this, i just have one more question that i just need your opinion on really.

    So, the server is in a constant loop checking for new data on all of the sockets connected with a 10 millisecond pause, I would just like to know is this one loop enough to handle about 30 clients max? The clients can view other clients details that the server will read from a file, given the correct command and send them, they can send messages in a 'room', they can also send private messages to other clients that use //PM:: to tell the server it's a private message so it should only be sent to one client, They will soon be able to transfer files, And i just keep thinking is there anyway the clients could possibly send to much for the server to handle at once?

  13. #28
    Its not rocket science vasanth's Avatar
    Join Date
    Jan 2002
    Posts
    1,683
    why dont you use the select statement.. its interrupt drive(imo)... its more efficient and does not waste cpu cycles...
    Last edited by vasanth; 10-18-2004 at 02:23 PM.

  14. #29
    Registered User
    Join Date
    Apr 2004
    Posts
    102
    I am using the Select statement, it's just that i thought maybe a thread for each client would be a better idea.

  15. #30
    Carnivore ('-'v) Hunter2's Avatar
    Join Date
    May 2002
    Posts
    2,879
    >>And i just keep thinking is there anyway the clients could possibly send to much for the server to handle at once?
    Isn't that the buffer overflow thing? Don't know much about it though.. Maybe the clients would just get errors (if non-blocking), or block, when they try to call send().
    Just Google It. √

    (\ /)
    ( . .)
    c(")(") This is bunny. Copy and paste bunny into your signature to help him gain world domination.

Page 2 of 3 FirstFirst 123 LastLast
Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Converting 32 bit binary IP to decimal IP (vice-versa)
    By Mankthetank19 in forum C Programming
    Replies: 15
    Last Post: 12-28-2009, 06:17 PM
  2. Extracting WAN IP out of a SOCKET
    By apsync in forum Windows Programming
    Replies: 13
    Last Post: 10-04-2008, 02:38 PM
  3. Problem while constructing IP packet and sending using socket() system call
    By cavestine in forum Networking/Device Communication
    Replies: 10
    Last Post: 10-15-2007, 05:49 AM
  4. IP without connecting to external socket
    By Hunter2 in forum Networking/Device Communication
    Replies: 5
    Last Post: 08-26-2003, 07:50 AM

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21