What is a simple C or C++ TCP server and client example?


Question

I need to quickly implement a very small C or C++ TCP server/client solution. This is simply to transfer literally an array of bytes from one computer to another - doesn't need to be scalable / over-complicated. The simpler the better. Quick and dirty if you can.

I tried to use the code from this tutorial, but I couldn't get it to build using g++ in Linux: http://www.linuxhowtos.org/C_C++/socket.htm

If possible, I'd like to avoid 3rd party libraries, as the system I'm running this on is quite restricted. This must be C or C++ as the existing application is already implemented.

Thanks to emg-2's answer, I managed to make the above mentioned code sample compatible with C++ using the following steps:

Add these headers to both client and server:

#include <cstdlib>
#include <cstring>
#include <unistd.h>

In server.c, change the type of clilen to socklen_t.

int sockfd, newsockfd, portno/*, clilen*/;
socklen_t clilen;

In client.c, change the following line:

if (connect(sockfd,&serv_addr,sizeof(serv_addr)) < 0) { ... }

To:

if (connect(sockfd,(const sockaddr*)&serv_addr,sizeof(serv_addr)) < 0)
1
41
2/19/2017 6:31:55 PM

Accepted Answer

I've used Beej's Guide to Network Programming in the past. It's in C, not C++, but the examples are good. Go directly to section 6 for the simple client and server example programs.

42
12/30/2017 1:17:09 PM

If the code should be simple, then you probably asking for C example based on traditional BSD sockets. Solutions like boost::asio are imho quite complicated when it comes to short and simple "hello world" example.

To compile examples you mentioned you must make simple fixes, because you are compiling under C++ compiler. I'm referring to following files:
http://www.linuxhowtos.org/data/6/server.c
http://www.linuxhowtos.org/data/6/client.c
from: http://www.linuxhowtos.org/C_C++/socket.htm

  1. Add following includes to both files:

    #include <cstdlib>
    #include <cstring>
    #include <unistd.h>
    
  2. In client.c, change the line:

    if (connect(sockfd,&serv_addr,sizeof(serv_addr)) < 0)
    { ... }
    

    to:

    if (connect(sockfd,(const sockaddr*)&serv_addr,sizeof(serv_addr)) < 0)
    { ... }
    

As you can see in C++ an explicit cast is needed.


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