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linuxsocketstcpboost-asiotcp-keepalive

IPPROTO_TCP or SOL_SOCKET

I have a simple P2P connection between my peers on a TCP socket. My client and server both are running on Linux. I have turned on TCP keep_alive functionality on my TCP sockets on both sides. I am using boost::asio to connect, read ane write data on my tcp sockets on both sides.

The tcp keep_alive expamples use IPPROTO_TCP and SOL_SOCKET which is confusing. Following are properties I set on my socket. But I am confused whether to use IPPROTO_TCP or SOL_SOCKET because both of them compile well on both the platforms.

Code: 

int on = 1;
setsockopt(socketNativeHandle, IPPROTO_TCP, TCP_NODELAY, &on, sizeof(int)
int timeOut = 3; //seconds
setsockopt(socketNativeHandle, IPPROTO_TCP, TCP_KEEPIDLE, &timeOut, sizeof(int)
setsockopt(socketNativeHandle, IPPROTO_TCP, TCP_KEEPINTVL, &timeOut, sizeof(int))
int unackCount = 1;
setsockopt(socketNativeHandle, IPPROTO_TCP, TCP_KEEPCNT, &unackCount, sizeof(int))

OR

int on = 1;
setsockopt(socketNativeHandle, SOL_SOCKET, TCP_NODELAY, &on, sizeof(int)
int timeOut = 3; //seconds
setsockopt(socketNativeHandle, SOL_SOCKET, TCP_KEEPIDLE, &timeOut, sizeof(int)
setsockopt(socketNativeHandle, SOL_SOCKET, TCP_KEEPINTVL, &timeOut, sizeof(int))
int unackCount = 1;
setsockopt(socketNativeHandle, SOL_SOCKET, TCP_KEEPCNT, &unackCount, sizeof(int))

Question:
Should I use SOL_SOCKET on both sides or should I use IPPROTO_TCP on both sides? Is there a way to decide this at runtime? Note that I have very simple peer to peer wifi connection.

Solution

  • SOL is abbreviation of socket_level, which designed for SO_* options, such as SO_REUSEPORT

    IPPROTO_* is designed for options of a specific network protocol, such as IPPROTO_IP, IPPROTO_TCP

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