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)
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
c
// 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
c
// 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
bash
# 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
c
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