Socket Programming for Games

Master low-level socket programming for custom game networking.

Socket Types

Type	Protocol	Use Case
SOCK_STREAM	TCP	Reliable data
SOCK_DGRAM	UDP	Real-time
SOCK_RAW	Raw IP	Custom protocols

BSD Socket (C)

#include <sys/socket.h>
#include <netinet/in.h>

int create_game_server(int port) {
    int sockfd = socket(AF_INET, SOCK_DGRAM, 0);

    struct sockaddr_in addr = {
        .sin_family = AF_INET,
        .sin_port = htons(port),
        .sin_addr.s_addr = INADDR_ANY
    };

    bind(sockfd, (struct sockaddr*)&addr, sizeof(addr));
    fcntl(sockfd, F_SETFL, O_NONBLOCK);

    return sockfd;
}

Socket Options

// Disable Nagle (reduce latency)
int flag = 1;
setsockopt(sockfd, IPPROTO_TCP, TCP_NODELAY, &flag, sizeof(flag));

// Enable address reuse
setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &flag, sizeof(flag));

// Set buffer size
int bufsize = 65536;
setsockopt(sockfd, SOL_SOCKET, SO_RCVBUF, &bufsize, sizeof(bufsize));

Byte Order

// Network byte order
uint16_t port_net = htons(8080);
uint32_t ip_net = htonl(ip_host);

// Host byte order
uint16_t port_host = ntohs(port_net);

Platform Differences

Feature	BSD	Winsock
Init	None	WSAStartup()
Close	close()	closesocket()
Error	errno	WSAGetLastError()
Non-block	fcntl()	ioctlsocket()

Troubleshooting

Common Failure Modes

Error	Root Cause	Solution
EADDRINUSE	Port in use	SO_REUSEADDR
ECONNRESET	Peer closed	Handle gracefully
EMFILE	Too many fds	Increase ulimit
High latency	Nagle	TCP_NODELAY

Debug Checklist

# Check listening sockets
netstat -tlnp | grep game-server

# Trace syscalls
strace -e socket,bind,connect ./game-server

# Monitor traffic
tcpdump -i lo port 8080

Unit Test Template

void test_socket_creation() {
    int fd = create_game_server(8080);
    assert(fd >= 0);

    struct sockaddr_in addr;
    socklen_t len = sizeof(addr);
    getsockname(fd, (struct sockaddr*)&addr, &len);
    assert(ntohs(addr.sin_port) == 8080);

    close(fd);
}

Resources

• assets/ - Socket templates
• references/ - Platform guides