GMS Linux: start?

2025-12-30 01:20:20 +00:00
commit ac241a9148
48 changed files with 2028 additions and 0 deletions
@@ -0,0 +1,15 @@
+TARGET = nc
+SRCS = nc.c
+CC = gcc
+CFLAGS = -static -Wall
+
+OUT_BIN ?= $(TARGET)
+
+all: $(OUT_BIN)
+
+$(OUT_BIN): $(SRCS)
+	@echo "   [CC] Compiling to $(OUT_BIN)..."
+	$(CC) $(CFLAGS) -o $@ $^
+
+clean:
+	rm -f $(TARGET)
@@ -0,0 +1,132 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+#include <sys/socket.h>
+#include <sys/select.h>
+#include <errno.h>
+
+#define BUF_SIZE 1024
+
+// 에러 처리 헬퍼
+void error_exit(char *msg) {
+    perror(msg);
+    exit(1);
+}
+
+void loop(int sockfd) {
+    fd_set read_fds;
+    char buf[BUF_SIZE];
+    int max_fd = sockfd > STDIN_FILENO ? sockfd : STDIN_FILENO;
+    int stdin_eof = 0; // [NEW] 입력 종료 여부 플래그
+
+    while (1) {
+        FD_ZERO(&read_fds);
+        
+        // [NEW] 입력이 아직 안 끝났을 때만 STDIN 감시
+        if (!stdin_eof) {
+            FD_SET(STDIN_FILENO, &read_fds);
+        }
+        FD_SET(sockfd, &read_fds); // 소켓은 항상 감시
+
+        if (select(max_fd + 1, &read_fds, NULL, NULL, NULL) < 0) {
+            if (errno == EINTR) continue;
+            error_exit("select");
+        }
+
+        // 1. 키보드/파일 입력 -> 소켓 전송
+        if (!stdin_eof && FD_ISSET(STDIN_FILENO, &read_fds)) {
+            int n = read(STDIN_FILENO, buf, BUF_SIZE);
+            
+            if (n < 0) error_exit("read stdin");
+            
+            if (n == 0) {
+                // [NEW] EOF(파일 끝) 도달 시: 
+                // 즉시 종료하지 않고, "나는 보낼 거 다 보냈다"고 표시만 함
+                stdin_eof = 1;
+                
+                // (선택사항) TCP Half-Close: 서버에게 "보낼 거 끝났다"고 알림
+                shutdown(sockfd, SHUT_WR); 
+            } else {
+                if (write(sockfd, buf, n) < 0) error_exit("write to socket");
+            }
+        }
+
+        // 2. 소켓 수신 -> 화면 출력
+        if (FD_ISSET(sockfd, &read_fds)) {
+            int n = read(sockfd, buf, BUF_SIZE);
+            
+            if (n < 0) error_exit("read socket");
+            
+            if (n == 0) {
+                // [NEW] 서버가 연결을 끊었을 때 비로소 루프 종료!
+                break; 
+            }
+            if (write(STDOUT_FILENO, buf, n) < 0) error_exit("write to stdout");
+        }
+    }
+}
+
+int main(int argc, char *argv[]) {
+    if (argc < 3) {
+        printf("Usage:\n");
+        printf("  Connect: nc <IP> <PORT>\n");
+        printf("  Listen : nc -l <PORT>\n");
+        return 1;
+    }
+
+    int sockfd;
+    struct sockaddr_in addr;
+    memset(&addr, 0, sizeof(addr));
+    addr.sin_family = AF_INET;
+
+    // --- Server Mode (-l) ---
+    if (strcmp(argv[1], "-l") == 0) {
+        int port = atoi(argv[2]);
+        int listen_fd = socket(AF_INET, SOCK_STREAM, 0);
+        if (listen_fd < 0) error_exit("socket");
+
+        // 주소 재사용 허용 (Time-wait 방지)
+        int opt = 1;
+        setsockopt(listen_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
+
+        addr.sin_addr.s_addr = htonl(INADDR_ANY);
+        addr.sin_port = htons(port);
+
+        if (bind(listen_fd, (struct sockaddr*)&addr, sizeof(addr)) < 0) error_exit("bind");
+        if (listen(listen_fd, 1) < 0) error_exit("listen");
+
+        printf("Listening on port %d...\n", port);
+        
+        struct sockaddr_in client_addr;
+        socklen_t client_len = sizeof(client_addr);
+        sockfd = accept(listen_fd, (struct sockaddr*)&client_addr, &client_len);
+        if (sockfd < 0) error_exit("accept");
+
+        printf("Connection from %s\n", inet_ntoa(client_addr.sin_addr));
+        close(listen_fd); // 더 이상 리스닝 안 함 (1:1 채팅)
+    } 
+    
+    // --- Client Mode ---
+    else {
+        char *ip = argv[1];
+        int port = atoi(argv[2]);
+
+        sockfd = socket(AF_INET, SOCK_STREAM, 0);
+        if (sockfd < 0) error_exit("socket");
+
+        addr.sin_port = htons(port);
+        if (inet_pton(AF_INET, ip, &addr.sin_addr) <= 0) error_exit("invalid address");
+
+        printf("Connecting to %s:%d...\n", ip, port);
+        if (connect(sockfd, (struct sockaddr*)&addr, sizeof(addr)) < 0) error_exit("connect");
+        printf("Connected!\n");
+    }
+
+    // 데이터 교환 루프 진입
+    loop(sockfd);
+
+    close(sockfd);
+    return 0;
+}