From 122a69f715acfe73963a2347cbb335e41bce944c Mon Sep 17 00:00:00 2001
From: Guangxiong Lin <hi@gxlin.org>
Date: Thu, 1 Dec 2022 16:08:38 +0800
Subject: Implement echo server with error handling

Implement echo server with error handling

Fix gitignore

Implement an echo server with error handling
---
 .gitignore |  2 ++
 Makefile   |  8 ++++----
 client.c   | 33 ++++++++++++++++++++++++++++++++-
 common.c   |  8 ++++++++
 common.h   |  1 +
 server.c   | 37 ++++++++++++++++++++++++++++++++++---
 6 files changed, 81 insertions(+), 8 deletions(-)
 create mode 100644 common.c
 create mode 100644 common.h

diff --git a/.gitignore b/.gitignore
index 5761abc..1c102fa 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1 +1,3 @@
 *.o
+client
+server
diff --git a/Makefile b/Makefile
index 7c005c9..eee72d1 100644
--- a/Makefile
+++ b/Makefile
@@ -10,8 +10,8 @@ clean:
 %.o: %.c
 	$(CC) -c $(CFLAGS) $(CPPFLAGS) $< -o $@
 
-client: client.o
-	$(CC) -o $@ $<
+client: client.o common.o
+	$(CC) -o $@ $^
 
-server: server.o
-	$(CC) -o $@ $<
+server: server.o common.o
+	$(CC) -o $@ $^
diff --git a/client.c b/client.c
index 82c35a6..9e3a421 100644
--- a/client.c
+++ b/client.c
@@ -1,11 +1,19 @@
 #include <sys/socket.h>
 #include <arpa/inet.h>
 #include <strings.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <stdbool.h>
+#include <stdio.h>
+
+#include "common.h"
 
 int
 main()
 {
     int sockfd = socket(AF_INET, SOCK_STREAM, 0);
+    if (sockfd == -1)
+        panic("socket creation error");
 
     struct sockaddr_in serv_addr;
     bzero(&serv_addr, sizeof(serv_addr));
@@ -13,5 +21,28 @@ main()
     serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
     serv_addr.sin_port = htons(8888);
 
-    connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr));
+    if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) == -1)
+        panic("socket connect error");
+
+    while (true) {
+        char buf[1024];
+        bzero(&buf, sizeof(buf));
+        scanf("%s", buf);
+        ssize_t n_write_bytes = write(sockfd, buf, sizeof(buf));
+        if (n_write_bytes == -1) {
+            printf("socket already disconnected, cannot write any more!\n");
+            break;
+        }
+
+        ssize_t n_read_bytes = read(sockfd, buf, sizeof(buf));
+        if (n_read_bytes > 0) {
+            printf("message from server: %s\n", buf);
+        } else if (n_read_bytes == 0) {
+            printf("server socket disconnected!\n");
+            break;
+        } else if (n_read_bytes == -1) {
+            close(sockfd);
+            panic("socket read error");
+        }
+    }
 }
diff --git a/common.c b/common.c
new file mode 100644
index 0000000..154e60d
--- /dev/null
+++ b/common.c
@@ -0,0 +1,8 @@
+#include <stdlib.h>
+#include <stdio.h>
+
+void panic(const char *msg)
+{
+    perror(msg);
+    exit(EXIT_FAILURE);
+}
diff --git a/common.h b/common.h
new file mode 100644
index 0000000..fbb7267
--- /dev/null
+++ b/common.h
@@ -0,0 +1 @@
+void panic(const char *);
diff --git a/server.c b/server.c
index 9e2fd5c..63f3062 100644
--- a/server.c
+++ b/server.c
@@ -1,11 +1,20 @@
 #include <netinet/in.h>
 #include <sys/socket.h>
 #include <arpa/inet.h>
-#include <string.h>
+#include <strings.h>
+#include <stdlib.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <sys/types.h>
+#include <unistd.h>
+
+#include "common.h"
 
 int main()
 {
     int sockfd = socket(AF_INET, SOCK_STREAM, 0);
+    if (sockfd == -1)
+        panic("socket creation error");
 
     struct sockaddr_in serv_addr;
     bzero(&serv_addr, sizeof(serv_addr));
@@ -13,14 +22,36 @@ int main()
     serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
     serv_addr.sin_port = htons(8888);
 
-    bind(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
+    if (bind(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) == -1)
+        panic("socket bind error");
 
-    listen(sockfd, SOMAXCONN);
+    if (listen(sockfd, SOMAXCONN) == -1)
+        panic("socket listen error");
 
     struct sockaddr_in clnt_addr;
     socklen_t clnt_addr_len = sizeof(clnt_addr);
     bzero(&clnt_addr, sizeof(clnt_addr));
+
     int clnt_sockfd = accept(sockfd, (struct sockaddr *)&clnt_addr, &clnt_addr_len);
+    if (clnt_sockfd == -1)
+        panic("socket accept error");
 
     printf("New client fd %d, ip: %s, port: %d\n", clnt_sockfd, inet_ntoa(clnt_addr.sin_addr), ntohs(clnt_addr.sin_port));
+
+    while (true) {
+        char buf[1024];
+        bzero(&buf, sizeof(buf));
+        ssize_t n_read_bytes = read(clnt_sockfd, buf, sizeof(buf));
+        if (n_read_bytes > 0) {
+            printf("message from client fd %d: %s\n", clnt_sockfd, buf);
+            write(clnt_sockfd, buf, sizeof(buf));
+        } else if (n_read_bytes == 0) {
+            printf("client fd %d disconnected\n", clnt_sockfd);
+            close(clnt_sockfd);
+            break;
+        } else if (n_read_bytes == -1) {
+            close(clnt_sockfd);
+            panic("socket read error");
+        }
+    }
 }
-- 
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