Problem with C ++ multithreaded TCP server

Question

I am writing a simple TCP server. The model I am is a server that accepts client connections on the main thread and passes them to another thread so that the server can listen on connections again. The following are the relevant parts of the code that I used:

Acceptance of connections:

void startServer () { int serverSideSocket = 0; int clientSideSocket = 0; serverSideSocket = socket(AF_INET, SOCK_STREAM, 0); if (serverSideSocket < 0) { error("ERROR opening socket"); exit(1); } clientAddressLength = sizeof(clientAddress); memset((char *) &serverAddress, 0, sizeof(serverAddress)); memset((char *) &clientAddress, 0, clientAddressLength); serverAddress.sin_family = AF_INET; serverAddress.sin_addr.s_addr = INADDR_ANY; serverAddress.sin_port = htons(32000); if (bind(serverSideSocket, (struct sockaddr *) &serverAddress, sizeof(serverAddress)) < 0) { error("ERROR on binding"); exit(1); } listen(serverSideSocket, SOMAXCONN); while(true) { clientSideSocket = accept(serverSideSocket, (struct sockaddr *) &clientAddress, &clientAddressLength); if (clientSideSocket < 0) error("ERROR on accept"); processingThreadGroup->create_thread(boost::bind(process, clientSideSocket, this)); } } 

Here, the ThreadGroup handler is an instance of boost :: thread_group. In the process method:

 void process (int clientSideSocket, DataCollector* collector) { int numberOfCharactersRead = 0; string buffer; do { char msgBuffer[1000]; numberOfCharactersRead = recv(clientSideSocket, msgBuffer, (1000 - 1), 0); if (numberOfCharactersRead < 0) { //display error close(clientSideSocket); } else if (numberOfCharactersRead == 0) close(clientSideSocket); else { printf("%s", msgBuffer); memset(msgBuffer, 0, 1000); } } while (numberOfCharactersRead > 0); } 

However, when I debug the code, I saw that when the processing thread was called, the main thread no longer accepts the connection. Data is read only inside the process () method. The main thread does not seem to work anymore. What is the problem with the approach I took and suggestions for fixing it?

EDIT: I think I found the problem here and updated it as an answer. I do not agree, as I answered my question. Thanks for helping everyone!

Answer 1

I think I found the problem. I used this as a server to receive syslog messages. The code I use for the syslog message generator looks like this:

 openlog ("MyProgram", LOG_CONS | LOG_PID | LOG_NDELAY, LOG_LOCAL0); cout << "opened the log" << endl; for (int i = 0 ; i < 10 ; i++) { syslog (LOG_INFO, "Program started by User %d \n", getuid ()); syslog (LOG_WARNING, "Beware of the WARNING! \n"); syslog (LOG_ERR, "fatal ERROR! \n"); } closelog (); cout << "closed the log" << endl; 

and I use the entry in the rsyslog.conf file to direct all the syslog LOG_LOCAL0 application traffic to be sent to the appropriate TCP port where the server is listening. One way or another, syslog allows you to create only one connection, not multiple connections. Therefore, he used only one connection in one thread. If this connection was closed, the new connection is terminated.

I checked with a regular tcp client. This works fine, with multiple streams generated for each received connection.