java - 错误: Connection refused when connecting to socket server

Question

当使用 3 个终端时，我有以下 C_Client 代码运行良好，2 个服务器和 1 个客户端。

但是，当我将同一套代码部署到3台不同的机器上时，它没有按预期执行。

场景很少，

我对 server1 使用 8888 端口，对 server2 使用 5678 端口。输入参数供客户端输入。

1. 在同一台机器上连接客户端和服务器 - 按预期工作带参数输入:127.0.0.1 127.0.0.1 8888 5678

2. 在同一台机器上连接client和server2，在其他机器上连接server1，它也可以工作，参数输入:192.168.28.116 127.0.0.1 8888 5678

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3. 有问题的场景，在不同的机器上连接client和server2，无论我做了什么(例如关闭所有防火墙，检查端口是否监听)，都会显示错误消息: 连接 tpserver 时出错:连接被拒绝。

参数输入:

192.168.28.116 192.168.28.117 8888 5678 或

127.0.0.7 192.168.28.117 8888 5678

从2开始，可以肯定server1上同一台机器或不同机器上的连接并不重要，但是当连接不同机器上的server2时，连接到server1套接字时奇怪地显示错误？为什么？

客户端.c

//Variable declaration
int sockfd, sockfd2, portno, portno2, n, a, pid, startonce;
struct sockaddr_in serv_addr, serv_addr2;
struct hostent *server, *server2; 

//Opening socket
portno = atoi(argv[3]);
portno2 = atoi(argv[4]);
sockfd = socket(AF_INET, SOCK_STREAM, 0);
sockfd2 = socket(AF_INET, SOCK_STREAM, 0);
if ((sockfd < 0) || (sockfd2 < 0)) {
    error("ERROR opening socket");
}
server = gethostbyname(argv[1]);
server2 = gethostbyname(argv[2]);
if (server == NULL){
    fprintf(stderr, "ERROR, no such host\n");
    exit(0);
}

//Serv_addr for tpServer
bzero((char *) &serv_addr, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length);
serv_addr.sin_port = htons(portno);
if (connect(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {    
    error("ERROR connecting tpserver");  
}

//Serv_addr for resultServer
bzero((char *) &serv_addr2, sizeof(serv_addr2));
serv_addr2 = serv_addr; 
serv_addr2.sin_port = htons(portno2);  
if (connect(sockfd2, (struct sockaddr *) &serv_addr2, sizeof(serv_addr2)) < 0) {    
    error("ERROR connecting resultserver");  
}

服务器1.c

//Declare variables here
int sockfd, newsockfd, portno, pid;
socklen_t clilen;
struct sockaddr_in serv_addr, cli_addr;
if (argc < 2) {
    fprintf(stderr, "ERROR, no port provided\n");
    exit(1);
}

//Opening socket
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0) {    
    error("ERROR opening socket");
}

//Filling info for serv_addr
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) {
    error("ERROR on binding");
}
listen(sockfd,5);
clilen = sizeof(cli_addr);

//Fork when there a successful connection
while (1) {
    newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
    if (newsockfd < 0) {
        error("ERROR on accept");
    }
    pid = fork();
    if (pid < 0) {
        error("ERROR on fork");
    }
    if (pid == 0) {
        close(sockfd);
        dostuff(newsockfd);
        exit(0);
    }
    else close(newsockfd);
}
close(sockfd);
return 0; 
}

Server2.java

public void startServer(final int portno) {
    try {
        ServerSocket serverSocket = new ServerSocket(portno);
        System.out.println("Waiting for clients to connect...");

        while (true) {                
            try {
                Socket clientSocket = serverSocket.accept();
                clientProcessingPool.submit(new ClientTask(clientSocket));
            }
            catch (IOException e) {
                System.err.println("Unable to process client request");
                e.printStackTrace();
            }
        }
    }
catch (IOException e) {
        System.err.println("Unable to process client request");
        e.printStackTrace();
    }       
}

更新2016/5/17 11:44

我更改了代码:

//Serv_addr for resultServer
bzero((char *) &serv_addr2, sizeof(serv_addr2));
serv_addr2 = serv_addr; //Copied tpServer socket to resultServer info for local testing
serv_addr2.sin_port = htons(portno2);  
if (connect(sockfd2, (struct sockaddr *) &serv_addr2, sizeof(serv_addr2)) < 0) {    
    error("ERROR connecting resultserver");  
}

至

//Serv_addr for resultServer
bzero((char *) &serv_addr2, sizeof(serv_addr2));
serv_addr2.sin_family = AF_INET;
bcopy((char *)server2->h_addr, (char *)&serv_addr2.sin_addr.s_addr, server2->h_length);
serv_addr2.sin_port = htons(portno2);  
if (connect(sockfd2, (struct sockaddr *) &serv_addr2, sizeof(serv_addr2)) < 0) {    
    error("ERROR connecting resultserver");  
}

但我仍然收到相同的错误消息:

./tp_client 192.168.28.152 192.168.28.130 8888 5678
ERROR connecting tpserver: Connection refused

更新2016/5/17 11:49

我尝试使用另一台Linux机器，它成功连接到两台服务器，但是当我在Windows上设置server2时，它仍然显示连接被拒绝。

那么现在，它可以在 3 个不同的 Linux 上运行，但不能在 Linux 到 Windows 上运行？我在 Windows 上使用浏览器测试了我的服务器，它的工作方式非常出色。如何将 Linux 客户端连接到 Windows 服务器？

更新2016/5/18 10:52

新发现，当客户端连接2个服务器时，2个ip必须相同，而不是在2个不同的服务器机器上，无论是否是windows。如果相同，则建立连接，如果不同，则连接被拒绝。我包含了 perror() 函数，但仍然收到相同的消息:连接被拒绝，当我在 client.c 中声明套接字时是否有任何问题？

Answer 1

所以最后发现方法:gethostbyname已被弃用，无法响应请求。更新为方法:getaddrinfo后，问题解决。

现在的代码:

客户端.c

int sockfd, sockfd2;
struct addrinfo hints, *servinfo, *p;
struct addrinfo hints2, *servinfo2, *p2;
int rv, rv2;
 //Opening socket
memset(&hints, 0, sizeof(hints));
memset(&hints2, 0, sizeof(hints2));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints2.ai_family = AF_UNSPEC;
hints2.ai_socktype = SOCK_STREAM;

if ((rv = getaddrinfo(argv[1], argv[3], &hints, &servinfo)) != 0) {
    fprintf(stderr, "tpgetaddrinfo: %s\n", gai_strerror(rv));
exit(1);
}

if ((rv2 = getaddrinfo(argv[2], argv[4], &hints2, &servinfo2)) != 0) {
fprintf(stderr, "rsgetaddrinfo: %s\n", gai_strerror(rv2));
exit(1);
}

for (p = servinfo; p != NULL; p = p->ai_next) {
if ((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1) {
    perror("tpsocket");
    continue;
}

if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) {
    perror("tpconnect");
    close(sockfd);
    continue;
}

break;
}

for (p2 = servinfo2; p2 != NULL; p2 = p2->ai_next) {
if ((sockfd2 = socket(p2->ai_family, p2->ai_socktype, p2->ai_protocol)) == -1) {
    perror("rssocket");
    continue;
}

if (connect(sockfd2, p2->ai_addr, p2->ai_addrlen) == -1) {
    perror("rsconnect");
    close(sockfd2);
    continue;
}

break;
}

if (p == NULL) {
fprintf(stderr, "failed to connect tpserver\n");
exit(2);
}

if (p2 == NULL) {
fprintf(stderr, "failed to connect rsserver\n");
exit(2);
}

freeaddrinfo(servinfo);
freeaddrinfo(servinfo2);