Intro
I was looking around for a sample TCP socket program written in C++ that might make working with TCP sockets less mysterious. I expected to find a flood of things to pick from, but that really wasn’t the case.
The Details
OK, I only looked for a few minutes, to be honest. The one I did settle on seems adequate. It’s sufficiently old, however, that it doesn’t actually work as-is. Probably if it did I wouldn’t even mention it. So I thought it was worth repeating here, with some tiny semantic updates.
What I used is from this web page: http://cs.baylor.edu/~donahoo/practical/CSockets/practical/. I was really only interested in the TCP echo client. It’s a good stand-ion for any TCP client I think.
Here’s TCPechoClient.cpp:
/* * C++ sockets on Unix and Windows * Copyright (C) 2002 * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, write to the Free Software * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA */ // taken from http://cs.baylor.edu/~donahoo/practical/CSockets/practical/TCPEchoClient.cpp #include "PracticalSocket.h" // For Socket and SocketException #include <iostream> // For cerr and cout #include <cstdlib> // For atoi() #include <cstring> // author forgot this using namespace std; const int RCVBUFSIZE = 32; // Size of receive buffer int main(int argc, char *argv[]) { if ((argc < 3) || (argc > 4)) { // Test for correct number of arguments cerr << "Usage: " << argv[0] << " <Server> <Echo String> [<Server Port>]" << endl; exit(1); } string servAddress = argv[1]; // First arg: server address char *echoString = argv[2]; // Second arg: string to echo // DrJ test // echoString = "GET / HTTP/1.0\n\n"; int echoStringLen = strlen(echoString); // Determine input length unsigned short echoServPort = (argc == 4) ? atoi(argv[3]) : 7; try { // Establish connection with the echo server TCPSocket sock(servAddress, echoServPort); // Send the string to the echo server sock.send(echoString, echoStringLen); char echoBuffer[RCVBUFSIZE + 1]; // Buffer for echo string + \0 int bytesReceived = 0; // Bytes read on each recv() int totalBytesReceived = 0; // Total bytes read // Receive the same string back from the server cout << "Received: "; // Setup to print the echoed string while (totalBytesReceived < echoStringLen) { // Receive up to the buffer size bytes from the sender if ((bytesReceived = (sock.recv(echoBuffer, RCVBUFSIZE))) <= 0) { cerr << "Unable to read"; exit(1); } totalBytesReceived += bytesReceived; // Keep tally of total bytes echoBuffer[bytesReceived] = '\0'; // Terminate the string! cout << echoBuffer; // Print the echo buffer } cout << endl; // Destructor closes the socket } catch(SocketException &e) { cerr << e.what() << endl; exit(1); } return 0; } |
Note the cstring header file I needed to include. The standard must have changed to require this since the original code was published.
Then I neeed PracticalSocket.h, but that has no changes from the original version: “http://cs.baylor.edu/~donahoo/practical/CSockets/practical/PracticalSocket.h, and his Makefile is also just fine: http://cs.baylor.edu/~donahoo/practical/CSockets/practical/Makefile. For the fun of it I also set up the TCP Echo Server: http://cs.baylor.edu/~donahoo/practical/CSockets/practical/TCPEchoServer.cpp.
Run
make TCPEchoclient
and you should be good to go. How to test this TCPEchoClient against your web server? I found that the following works:
~/TCPEchoClient drjohnstechtalk.com 'GET / HTTP/1.0 Host: drjohnstechtalk.com ' 80 |
which gives this output:
Received: HTTP/1.1 301 Moved Permanently Date: Thu, 23 Feb 2012 17:19:02 |
which, now that I analyze it, looks cut-off. Hmm. Because with curl I have:
curl -i drjohnstechtalk.com
HTTP/1.1 301 Moved Permanently Date: Thu, 23 Feb 2012 17:19:43 GMT Server: Apache/2.2.16 (Ubuntu) X-Powered-By: PHP/5.3.3-1ubuntu9.5 Location: http://www.drjohnstechtalk.com/blog/ Vary: Accept-Encoding Content-Length: 2 Content-Type: text/html |
I guess that’s what you get for demo code. At this point I don’t have a need to sort it out so I won’t. Perhaps we’ll come back to it later. Looking at it, I see the received buffer size is quite small, 32 bytes. I tried to set that to a reasonable value, 200 MBytes, but get a segmentation fault. The largest I could manage, after experiementation, is 10000000 bytes:
//const int RCVBUFSIZE = 32; // Size of receive buffer const int RCVBUFSIZE = 10000000; // Size of receive buffer - why is 10 MB the max. value?? |
and this does indeed give us the complete output from our web server home page now.
Conclusion
There is some demo C++ code which creates a useable class for dealing with TCP sockets. There might be some work to do before it could be used in a serious application, however.
One reply on “C++ TCP Socket Program”
Hi Dr John,
thanks a lot for this example.
I try to compile it with VS 2010 on an win 7 machine 64 bit.
I got PracticalSocket.h and PracticalSocket.cpp and inserted them in the project.
My attempt to compile it for win32 fails because of many linker errors here just one example.
PracticalSocket.obj : error LNK2019: unresolved external symbol _socket@12 referenced in function “protected: __thiscall Socket::Socket(int,int)” (??0Socket@@IAE@HH@Z)
do you have any idea how to fix it?
have you an idea how long would the latency of the socket be?
Thanks a lot in advance
All the best
kinor