add solution

solutions/sur/async/chat.c

@@ -0,0 +1,72 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <sys/select.h>
+#include <limits.h>
+
+const int N = 256;
+
+int fd; 
+char *fifo = "/tmp/fifo"; 
+char buf1[N], buf2[N]; 
+fd_set set;
+
+void proc_write() {
+    fd = open(fifo, O_WRONLY); 
+    FD_ZERO(&set);
+    FD_SET(fd, &set);
+    fgets(buf2, N, stdin); 
+    int res_select = select(fd + 1, NULL, &set, NULL, NULL);
+    if (res_select != 0 && res_select != -1) {
+       write(fd, buf2, strlen(buf2)+1); 
+    }
+    close(fd); 
+}
+
+void proc_read() {
+    fd = open(fifo, O_RDONLY); 
+    FD_ZERO(&set);
+    FD_SET(fd, &set);
+    int res_select = select(fd + 1, &set, NULL, NULL, NULL);
+    if (res_select != 0 && res_select != -1) {
+        read(fd, buf1, sizeof(buf1)); 
+        printf("User2: %s\n", buf1); 
+    }
+    close(fd); 
+}
+
+int main(int argc, char **argv) 
+{ 
+
+    /*
+    Usage: argc >= 1 && argv[1] is id
+    in one terminal ./chat 1
+    on second terminal ./chat 2
+    user with id = 1 starts the communication
+    */
+
+    if (argc < 2) {
+        puts("arc should be more than one (id)");
+        exit(1);
+    }
+
+    int id = atoi(argv[1]);
+
+    mkfifo(fifo, 0666); 
+
+    while (1) { 
+        if (id == 1) {
+            proc_write();
+            proc_read();
+        } else {
+            proc_read();
+            proc_write();
+        }
+    } 
+
+    return 0; 
+}