linux socket连接中 ERRNO错误

Connection refused：应该是连接的服务端没有启动或者连接端口错误，可以用如下代码测试

client端：

 #include <stdio.h>
 #include <sys/types.h>          /* See NOTES */
 #include <sys/socket.h>
 #include <strings.h>
 #include <unistd.h>
 #include <netinet/in.h>
 #include <string.h>
 #include <arpa/inet.h>
 #include <errno.h>
 #define PORT 1234
 #define SERVER "10.1.70.21"

 int main()
 {
         int fd = socket(AF_INET, SOCK_STREAM, );
         int nfd;
         int ret;
         struct sockaddr_in server_addr, client_addr;
         bzero(&server_addr, sizeof(server_addr));

         server_addr.sin_family =AF_INET;
         server_addr.sin_port = htons(PORT);
         inet_pton(AF_INET, SERVER, &server_addr.sin_addr);
         //bind(fd, (struct sockaddr *)&server_addr, sizeof(server_addr));
         errno = ;
         ret = connect(fd, (struct sockaddr*)&server_addr, sizeof(server_addr));
         if(ret == -)
         {
                 perror("connect: ");
         }
         char buf[];
         while()
         {
                 bzero(buf, );
                 ret = read(STDIN_FILENO, buf, sizeof(buf));
                 printf("ret: %d, buf: %s", ret, buf);
                 ret = write(fd, buf, ret);
                 printf("ret:%d\n", ret);
                 if(ret < )
                 {
                         perror("write error");
                 }
                 ret = read(fd, buf, );
                 if(ret < )
                 {
                         perror("ret");
                 }
                 write(STDOUT_FILENO, buf, ret);
         }
         return ;
 }

server端：

　　

 #include <stdio.h>
 #include <sys/types.h>          /* See NOTES */
 #include <sys/socket.h>
 #include <strings.h>
 #include <unistd.h>
 #include <netinet/in.h>
 #include <string.h>
 #include <errno.h>
 //server端监听端口
 #define PORT 3388
 int main()
 {
     int fd = socket(AF_INET, SOCK_STREAM, );//创建一个socket
     int nfd;
     struct sockaddr_in server_addr, client_addr;
     bzero(&server_addr, sizeof(server_addr));
     server_addr.sin_family =AF_INET; //ipv4
     server_addr.sin_port = htons(PORT);//端口
     server_addr.sin_addr.s_addr = htonl(INADDR_ANY);//监听本主机的所有ip

     bind(fd, (struct sockaddr *)&server_addr, sizeof(server_addr));//绑定
     listen(fd, );//监听socket连接，30为三次握手队列大小
     char buf[];
     // 把server_addr.sin_addr的地址转换成字符串（点分十进制表示）
     inet_ntop(AF_INET, &server_addr.sin_addr, buf, sizeof(buf));
     printf("%s\n", buf);//一般输出为0.0.0.0
     pid_t pid;
     while()
     {
         bzero(buf, sizeof(buf));//buf清零，相当于memset(buf, 0, sizeof(buf));

         socklen_t len= sizeof(client_addr);
         nfd = accept(fd, (struct sockaddr*)&client_addr, &len);//接收socket连接
         inet_ntop(AF_INET, &client_addr.sin_addr, buf, sizeof(buf));//获取socket连接客户端的ip
         printf("accept connetc %s port %d\n", buf, ntohs(client_addr.sin_port));    

         pid = fork();
         //子进程
         if(pid == )
         {
             while()
             {

                 int ret = read(nfd, buf, sizeof(buf));
                 if(ret <= )
                 {
                     perror("ret");
                     return ;
                 }
                 write(STDOUT_FILENO, buf, ret);
                 write(nfd, buf, ret);
             }
         }
     }
     return ;
 }