Comparing string data received from a socket in C

Question

I have a question on sockets. I have this code:

while(bytes = recv(sClient, cClientMessage, 599, 0)){

This puts the message it recives into cClientMessage and the message is always "Message". How I made an if statement like if(cClientMessage == "Message"){//do func}. Now this code will not do the function I want. I think this is because it's not receiving the message right. Can someone help me?

Answer 1

First there is a bug in the code you wrote:

while(bytes = recv(sClient, cClientMessage, 599, 0)){

This is wrong because recv will return non zero if there is a socket error and your code will lead to an infinite loop. In particular you want to check for > 0

char cClientMessage[599];
while((bytes = recv(sClient, cClientMessage, sizeof(cClientMessage), 0)) > 0)
{
  if(strlen("Message") == bytes && !strncmp("Message", cClientMessage, bytes))
  {
    //cClientMesssage contains "Message"
  }
} 

if(bytes == 0)
{
  //socket was gracefully closed
}
else if(bytes < 0)
{
  //socket error occurred
}

The problem with what you did: cClientMessage == "Message" is that if you compare a char* to a string literal, or a char[] to a string literal, then you will be comparing the pointer addresses and not the actual content.

Answer 2

Try:

if( strcmp( cClientMessage, "Message")) == 0 ) {
   // do something
}

Edit, following suggestion from strager:

A better solution, which does not depend on the received data being null terminated is to use memcmp:

if( memcmp( cClientMessage, "Message", strlen( "Message") )) == 0 ) {
   // do something
}