1 | #include <stdlib.h>
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2 | #include <netdb.h>
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3 | #include <sys/select.h>
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4 | #include <stdio.h>
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5 | #include <errno.h>
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6 | #include <fcntl.h>
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7 |
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8 | static struct sockaddr_storage pgStatAddr;
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9 |
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10 | typedef int bool;
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11 |
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12 | bool
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13 | set_noblock(int sock)
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14 | {
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15 | return (fcntl(sock, F_SETFL, O_NONBLOCK) != -1);
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16 | }
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17 |
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18 | void
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19 | socket_test_send_recv(void)
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20 | {
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21 |
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22 | int pgStatSock = -1;
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23 | socklen_t alen;
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24 | struct addrinfo *addrs = NULL,
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25 | *addr,
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26 | hints;
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27 | int ret;
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28 | fd_set rset;
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29 | struct timeval tv;
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30 | char test_byte;
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31 | int sel_res;
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32 | bool retry = 1;
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33 | int len;
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34 |
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35 | #define TESTBYTEVAL ((char) 199)
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36 |
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37 | /*
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38 | * Create the UDP socket for sending and receiving statistic messages
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39 | */
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40 | hints.ai_flags = AI_PASSIVE;
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41 | hints.ai_family = PF_UNSPEC;
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42 | hints.ai_socktype = SOCK_DGRAM;
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43 | hints.ai_protocol = 0;
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44 | hints.ai_addrlen = 0;
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45 | hints.ai_addr = NULL;
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46 | hints.ai_canonname = NULL;
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47 | hints.ai_next = NULL;
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48 | ret = getaddrinfo("localhost", NULL, &hints, &addrs);
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49 | if (ret || !addrs) {
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50 | printf("could not resolve \"localhost\": %s\n", gai_strerror(ret));
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51 | }
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52 | else {
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53 |
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54 | /*
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55 | * Loop through the results to try and find a working address.
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56 | */
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57 | for (addr = addrs; addr; addr = addr->ai_next)
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58 | {
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59 | /*
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60 | * Create the socket.
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61 | */
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62 | if ((pgStatSock = socket(addr->ai_family, SOCK_DGRAM, 0)) == -1)
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63 | {
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64 | printf("could not create socket for statistics collector\n");
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65 | continue;
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66 | }
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67 |
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68 | /*
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69 | * Bind it to a kernel assigned port on localhost and get the assigned
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70 | * port via getsockname().
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71 | */
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72 | if (bind(pgStatSock, addr->ai_addr, addr->ai_addrlen) < 0)
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73 | {
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74 | printf("could not bind socket for statistics collector\n");
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75 | closesocket(pgStatSock);
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76 | pgStatSock = -1;
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77 | continue;
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78 | }
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79 |
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80 | alen = sizeof(pgStatAddr);
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81 | if (getsockname(pgStatSock, (struct sockaddr *) & pgStatAddr, &alen) < 0)
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82 | {
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83 | printf("could not get address of socket for statistics collector\n");
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84 | closesocket(pgStatSock);
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85 | pgStatSock = -1;
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86 | continue;
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87 | }
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88 |
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89 | /*
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90 | * Connect the socket to its own address. This saves a few cycles by
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91 | * not having to respecify the target address on every send. This also
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92 | * provides a kernel-level check that only packets from this same
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93 | * address will be received.
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94 | */
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95 | if (connect(pgStatSock, (struct sockaddr *) & pgStatAddr, alen) < 0)
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96 | {
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97 | printf("could not connect socket for statistics collector\n");
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98 | closesocket(pgStatSock);
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99 | pgStatSock = -1;
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100 | continue;
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101 | }
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102 |
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103 | /*
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104 | * Try to send and receive a one-byte test message on the socket. This
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105 | * is to catch situations where the socket can be created but will not
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106 | * actually pass data (for instance, because kernel packet filtering
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107 | * rules prevent it).
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108 | */
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109 | test_byte = TESTBYTEVAL;
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110 |
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111 | while (retry) {
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112 | if (send(pgStatSock, &test_byte, 1, 0) != 1) {
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113 | /* if not interrupted, bail out */
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114 | if (errno != EINTR) {
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115 | retry = 0;
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116 | printf("could not send test message on socket for statistics collector\n");
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117 | closesocket(pgStatSock);
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118 | pgStatSock = -1;
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119 | continue;
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120 | }
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121 | }
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122 | else {
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123 | retry = 0;
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124 | }
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125 | }
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126 |
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127 | /*
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128 | * There could possibly be a little delay before the message can be
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129 | * received. We arbitrarily allow up to half a second before deciding
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130 | * it's broken.
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131 | */
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132 | for (;;) /* need a loop to handle EINTR */
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133 | {
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134 | FD_ZERO(&rset);
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135 | FD_SET(pgStatSock, &rset);
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136 |
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137 | tv.tv_sec = 0;
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138 | tv.tv_usec = 500000;
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139 | sel_res = select(pgStatSock + 1, &rset, NULL, NULL, &tv);
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140 | if (sel_res >= 0 || errno != EINTR)
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141 | break;
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142 | }
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143 | if (sel_res < 0)
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144 | {
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145 | printf("select() failed in statistics collector\n");
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146 | closesocket(pgStatSock);
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147 | pgStatSock = -1;
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148 | continue;
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149 | }
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150 | if (sel_res == 0 || !FD_ISSET(pgStatSock, &rset))
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151 | {
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152 | /*
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153 | * This is the case we actually think is likely, so take pains to
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154 | * give a specific message for it.
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155 | *
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156 | * errno will not be set meaningfully here, so don't use it.
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157 | */
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158 | printf("test message did not get through on socket for statistics collector\n");
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159 | closesocket(pgStatSock);
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160 | pgStatSock = -1;
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161 | continue;
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162 | }
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163 |
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164 | test_byte++; /* just make sure variable is changed */
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165 |
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166 | retry = 1;
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167 | while (retry) {
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168 | if (recv(pgStatSock, &test_byte, 1, 0) != 1) {
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169 | /* if not interrupted, bail out */
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170 | if (errno != EINTR) {
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171 | retry = 0;
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172 | printf("Errno: %i\n", errno);
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173 | printf("String error: %s\n", strerror(errno));
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174 | printf("could not receive test message on socket for statistics collector\n");
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175 | closesocket(pgStatSock);
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176 | pgStatSock = -1;
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177 | continue;
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178 | }
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179 | }
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180 | else {
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181 | retry = 0;
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182 | }
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183 | }
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184 |
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185 | if (test_byte != TESTBYTEVAL) /* strictly paranoia ... */
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186 | {
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187 | printf("incorrect test message transmission on socket for statistics collector\n");
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188 | closesocket(pgStatSock);
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189 | pgStatSock = -1;
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190 | continue;
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191 | }
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192 |
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193 | /* If we get here, we have a working socket */
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194 | printf("We have a working socket!\n");
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195 |
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196 | /*
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197 | * Set the socket to non-blocking IO.
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198 | */
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199 | if (!set_noblock(pgStatSock))
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200 | {
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201 | printf("could not set statistics collector socket to nonblocking mode\n");
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202 | }
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203 | else
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204 | {
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205 |
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206 | /* Try to read from it again without any data waiting... */
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207 | len = recv(pgStatSock, &test_byte, 1, 0);
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208 |
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209 | if (len < 0)
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210 | {
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211 | if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR) {
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212 | printf("Breaking out of loop. No data as expected\n");
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213 | break; /* out of inner loop */
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214 | }
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215 | printf("Unexpected error: %s\n", strerror(errno));
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216 | break;
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217 | }
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218 | else {
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219 | printf("Received data! Should not be possible\n");
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220 | }
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221 | }
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222 |
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223 | if (pgStatSock > -1) {
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224 | closesocket(pgStatSock);
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225 | }
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226 |
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227 | break;
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228 | }
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229 | }
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230 |
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231 | if (addrs != NULL)
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232 | freeaddrinfo(addrs);
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233 |
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234 | }
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235 |
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236 | int main(int argc, char **argv) {
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237 |
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238 | socket_test_send_recv();
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239 |
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240 | return 0;
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241 |
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242 | }
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