make it so

.gitignore

@@ -0,0 +1 @@
+bin/

Makefile

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+TARGET=868
+BUILDDIR=bin/
+PREFIX=/usr/local/bin/
+MAIN=main.c
+override CFLAGS+=-Werror -Wall -g -fPIC -O2 -DNDEBUG -ftrapv -Wfloat-equal -Wundef -Wwrite-strings -Wuninitialized -pedantic -std=gnu11
+
+all: main.c
+	mkdir -p $(BUILDDIR)
+	$(CC) $(MAIN) -o $(BUILDDIR)$(TARGET) $(CFLAGS)
+
+install: all
+	install $(BUILDDIR)$(TARGET) $(PREFIX)$(TARGET)
+
+uninstall:
+	rm -rf $(PREFIX)$(TARGET)

README.md

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+# 868
+
+An implementation of [RFC 868](https://tools.ietf.org/html/rfc862), the “time”
+service, for the heck of it.
+
+## Limitations
+
+I’m not sure this is actually correct.

main.c

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+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include <unistd.h>
+#include <netinet/in.h>
+
+void die(const char *msg) {
+    perror(msg);
+    exit(1);
+}
+
+int32_t get_date() {
+  int32_t res;
+
+  res = time(NULL);
+  res += 2208988800; // epoch to braindead format
+
+  return res;
+}
+
+int main(int argc, char *argv[]) {
+  int sockfd;
+  int newsockfd;
+  int port = 37;
+  socklen_t clilen;
+  struct sockaddr_in serv_addr, cli_addr;
+  int n;
+  int32_t date;
+
+  sockfd = socket(AF_INET, SOCK_STREAM, 0);
+  if (sockfd < 0) die("error opening socket.");
+
+  bzero((char *) &serv_addr, sizeof(serv_addr));
+  serv_addr.sin_family = AF_INET;
+  serv_addr.sin_addr.s_addr = INADDR_ANY;
+  serv_addr.sin_port = htons(port);
+
+  if (bind(sockfd, (struct sockaddr *) &serv_addr,
+           sizeof(serv_addr)) < 0) die("error binding socket.");
+
+  clilen = sizeof(cli_addr);
+
+  while (1) {
+    listen(sockfd, 5);
+
+    newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
+    if (newsockfd < 0) die("error accepting");
+
+    date = get_date();
+    n = write(newsockfd, &date, 4);
+    if (n < 0) die("error writing");
+    close(newsockfd);
+  }
+
+  close(sockfd);
+  return 0;
+}